Selenium nanoparticles inhibit Staphylococcus aureus growth

Staphylococcus aureus is a key bacterium commonly found in numerous infections. S. aureus infections are difficult to treat due to their biofilm formation and documented antibiotic resistance. While selenium has been used for a wide range of applications including anticancer applications, the effects of selenium nanoparticles on microorganisms remain largely unknown to date. The objective of this in vitro study was thus to examine the growth of S. aureus in the presence of selenium nanoparticles. Results of this study provided the first evidence of strongly inhibited growth of S. aureus in the presence of selenium nanoparticles after 3, 4, and 5 hours at 7.8, 15.5, and 31 μg/mL. The percentage of live bacteria also decreased in the presence of selenium nanoparticles. Therefore, this study suggests that selenium nanoparticles may be used to effectively prevent and treat S. aureus infections and thus should be further studied for such applications

Conformal Nanocarbon Coating of Alumina Nanocrystals for Biosensing and Bioimaging

A conformal coating technique with nanocarbon was developed to enhance the surface properties of alumina nanoparticles for bio-applications. The ultra-thin carbon layer induces new surface properties such as water dispersion, cytocompatibility and tuneable surface chemistry, while maintaining the optical properties of the core particle. The possibility of using these particles as agents for DNA sensing was demonstrated in a competitive assay. Additionally, the inherent fluorescence of the core alumina particles provided a unique platform for localization and monitoring of living organisms, allowing simultaneous cell monitoring and intra-cellular sensing. Nanoparticles were able to carry genes to the cells and release them in an environment where specific biomarkers were present.Comment: 11 pages, 5 figures, Supporting Informatio

Differential effects of nanoselenium doping on healthy and cancerous osteoblasts in coculture on titanium

In the present study, selenium (Se) nanoclusters were grown through heterogeneous nucleation on titanium (Ti) surfaces, a common orthopedic implant material. Normal healthy osteoblasts (bone-forming cells) and cancerous osteoblasts (osteosarcoma) were cultured on the Se-doped surfaces having three different coating densities. For the first time, it is shown that substrates with Se nanoclusters promote normal osteoblast proliferation and inhibit cancerous osteoblast growth in both separate (mono-culture) and coculture experiment. This study suggests that Se surface nanoclusters can be properly engineered to inhibit bone cancer growth while simultaneously promoting the growth of normal bone tissue

Simulation of a Safe Start-Up Maneuver for a Brayton Heat Pump

With about 50 % of the final energy used as heat in Europe, reducing fossil fuel consumption in this sector is crucial to achieve significant greenhouse gas emission reduction. Heat pumps using renewable electricity can potentially cover the heat demand below 500 °C. The DLR’s prototype CoBra (Cottbus Brayton cycle heat pump) aims at demonstrating the feasibility of a turbomachine driven closed-loop Brayton cycle heat pump with a thermal output of 200 kW and a heat sink temperature of up to 350 °C. In order to achieve safe operation, transient operation of the heat pump, such as start-up, must be analyzed. Temperature gradients must be kept below a limit, defined mostly by thermal stresses in the heat exchangers. At the same time, compressor surge and resonant frequencies of rotating components must be avoided during transient maneuvers of the system. In the current work, the heat pump prototype has been modeled with Modelica based on the component geometries and with the use of compressor and turbine maps obtained from 3D CFD simulations. For the start-up of the prototype, a suitable control strategy is developed and analyzed in order to minimize operational risks. Control parameters are compressor shaft speed, secondary mass flows and the turbine bypass. It is shown that a turbine bypass is necessary to avoid compressor surge during start-up. The conflicting requirements of crossing natural frequencies quickly while ensuring tolerable temperature gradients in the heat exchangers can be met. The results also show that pressure rise delay through volume dynamics is in the order of seconds. Slow transient effects in the evolution of fluid and heat exchanger temperatures arise from the thermal inertia of the heat exchangers

Part Load Capability of a High Temperature Heat Pump with Reversed Brayton Cycle

This paper studies the part load behavior and capability of a high temperature heat pump that operates with the Brayton cycle. A novel concept of a high temperature heat pump which is currently under construction in Cottbus (Germany) is presented. It goes far beyond temperature levels of current high temperature heat pumps and will provide process heat at above 250 °C. The heat pump uses a closed Brayton cycle driven by axial turbomachinery and provides up to 200 kW of thermal energy. The thermal output can be adjusted by variation of compressor shaft speed, use of internal recuperation and additionally by variation of the fluid inventory. The latter allows operation of our prototype within a broad part load range down to 25 % of the nominal power at nearly constant efficiencies and output temperatures. Brayton cycle heat pumps can be adapted to a wide range of industrial processes and enable highly efficient thermal energy storage systems to balance grid fluctuations

Modelling of Two-Phase Water Ejector in Rankine Cycle High Temperature Heat Pumps

Industrial high temperature heat pumps (HTHPs) can provide carbon-free process heat when operated with renewable energy sources. Using water as the working medium greatly increases the possible range of operation without the detrimental effects of traditional working fluids. One main challenge with this type of heat pump is the high compression ratio required to achieve a given temperature lift. As a result, water based heat pumps need several compression stages. Furthermore, the steam leaving the compressor is highly superheated. Ejectors driven by high pressure condensate allow to de-superheat the steam from the compressor outlet while simultaneously increasing its pressure. Thereby, the required power for compression as well as the number of compression stages can be reduced. This paper studies how the implementation of the two-phase water ejector influences the thermodynamic performance of Rankine cycle HTHP using a thermodynamic model of the ejector. Several cycle architectures are developed to study the ejector integration in the heat pump cycle, including traditional single-stage and multi-stage cycles. The cycles studies are conducted in the Modelica language, in the Modelon Impact environment. The study aims at informing about new developments in two-phase water ejectors and their application potential in Rankine cycle HTHPs. First simulations suggest an efficiency improvement of about 10% through the use of an ejector in the heat pump cycle

Transient analysis and control of a Brayton heat pump during start-up

This paper aims to investigate the transient response of the DLR's CoBra prototype, an innovative Brayton-cycle heat pump intended to provide heat above 250 °C and currently under commissioning at the DLR facility in Cottbus, Germany. First, a comprehensive transient thermodynamic model of the system is developed, accounting for heat exchangers and piping thermal inertia. Furthermore, a control logic is presented that ensures safe operation throughout off-design conditions and start-up manoeuvres. In particular, several control parameters are considered to avoid potential operational issues, such as critical temperature gradients, compressor surge, and critical mechanical vibration phenomena due to resonance. The performed simulations aim to reduce start-up time and energy consumed during start-up. Results show that with the help of the described controller, the system can reach design operation via a transient trajectory safely and quickly. Therefore, the capability of the CoBra prototype to flexibly supply high-temperature heat is demonstrated

Combination Antifungal Therapy for Cryptococcal Meningitis

Background Combination antifungal therapy (amphotericin B deoxycholate and flucytosine) is the recommended treatment for cryptococcal meningitis but has not been shown to reduce mortality, as compared with amphotericin B alone. We performed a randomized, controlled trial to determine whether combining flucytosine or high-dose fluconazole with high-dose amphotericin B improved survival at 14 and 70 days. Methods We conducted a randomized, three-group, open-label trial of induction therapy for cryptococcal meningitis in patients with human immunodeficiency virus infection. All patients received amphotericin B at a dose of 1 mg per kilogram of body weight per day; patients in group 1 were treated for 4 weeks, and those in groups 2 and 3 for 2 weeks. Patients in group 2 concurrently received flucytosine at a dose of 100 mg per kilogram per day for 2 weeks, and those in group 3 concurrently received fluconazole at a dose of 400 mg twice daily for 2 weeks. Results A total of 299 patients were enrolled. Fewer deaths occurred by days 14 and 70 among patients receiving amphotericin B and flucytosine than among those receiving amphotericin B alone (15 vs. 25 deaths by day 14; hazard ratio, 0.57; 95% confidence interval [CI], 0.30 to 1.08; unadjusted P=0.08; and 30 vs. 44 deaths by day 70; hazard ratio, 0.61; 95% CI, 0.39 to 0.97; unadjusted P=0.04). Combination therapy with fluconazole had no significant effect on survival, as compared with monotherapy (hazard ratio for death by 14 days, 0.78; 95% CI, 0.44 to 1.41; P=0.42; hazard ratio for death by 70 days, 0.71; 95% CI, 0.45 to 1.11; P=0.13). Amphotericin B plus flucytosine was associated with significantly increased rates of yeast clearance from cerebrospinal fluid (−0.42 log10 colony-forming units [CFU] per milliliter per day vs. −0.31 and −0.32 log10 CFU per milliliter per day in groups 1 and 3, respectively; P<0.001 for both comparisons). Rates of adverse events were similar in all groups, although neutropenia was more frequent in patients receiving a combination therapy. Conclusions Amphotericin B plus flucytosine, as compared with amphotericin B alone, is associated with improved survival among patients with cryptococcal meningitis. A survival benefit of amphotericin B plus fluconazole was not found

Intensified Antituberculosis Therapy in Adults with Tuberculous Meningitis

BACKGROUND Tuberculous meningitis is often lethal. Early antituberculosis treatment and adjunctive treatment with glucocorticoids improve survival, but nearly one third of patients with the condition still die. We hypothesized that intensified antituberculosis treatment would enhance the killing of intracerebral Mycobacterium tuberculosis organisms and decrease the rate of death among patients. METHODS We performed a randomized, double-blind, placebo-controlled trial involving human immunodeficiency virus (HIV)-infected adults and HIV-uninfected adults with a clinical diagnosis of tuberculous meningitis who were admitted to one of two Vietnamese hospitals. We compared a standard, 9-month antituberculosis regimen (which included 10 mg of rifampin per kilogram of body weight per day) with an intensified regimen that included higher-dose rifampin (15 mg per kilogram per day) and levofloxacin (20 mg per kilogram per day) for the first 8 weeks of treatment. The primary outcome was death by 9 months after randomization. RESULTS A total of 817 patients (349 of whom were HIV-infected) were enrolled; 409 were randomly assigned to receive the standard regimen, and 408 were assigned to receive intensified treatment. During the 9 months of follow-up, 113 patients in the intensified-treatment group and 114 patients in the standard-treatment group died (hazard ratio, 0.94; 95% confidence interval, 0.73 to 1.22; P=0.66). There was no evidence of a significant differential effect of intensified treatment in the overall population or in any of the subgroups, with the possible exception of patients infected with isoniazid-resistant M. tuberculosis. There were also no significant differences in secondary outcomes between the treatment groups. The overall number of adverse events leading to treatment interruption did not differ significantly between the treatment groups (64 events in the standard-treatment group and 95 events in the intensified-treatment group, P=0.08). CONCLUSIONS Intensified antituberculosis treatment was not associated with a higher rate of survival among patients with tuberculous meningitis than standard treatment. (Funded by the Wellcome Trust and the Li Ka Shing Foundation; Current Controlled Trials number, ISRCTN61649292.)