The rapid emergence of antibiotic-resistant bacterial “superbugs” with concomitant treatment failure and high mortality rates presents a severe threat to global health. The superbug risk is further ...exacerbated by chronic infections generated from antibiotic-resistant biofilms that render them refractory to available treatments. We hypothesized that efficient antimicrobial agents could be generated through careful engineering of hydrophobic and cationic domains in a synthetic semirigid polymer scaffold, mirroring and amplifying attributes of antimicrobial peptides. We report the creation of polymeric nanoparticles with highly efficient antimicrobial properties. These nanoparticles eradicate biofilms with low toxicity to mammalian cells and feature unprecedented therapeutic indices against red blood cells. Most notably, bacterial resistance toward these nanoparticles was not observed after 20 serial passages, in stark contrast to clinically relevant antibiotics where significant resistance occurred after only a few passages.
The Last Glacial Maximum Clark, Peter U.; Dyke, Arthur S.; Shakun, Jeremy D. ...
Science (American Association for the Advancement of Science),
08/2009, Letnik:
325, Številka:
5941
Journal Article
Recenzirano
We used 5704 ¹⁴C, ¹⁰Be, and ³He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial Maximum (LGM) in terms of global ice-sheet and ...mountain-glacier extent. Growth of the ice sheets to their maximum positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO₂. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level ∼14.5 ka.
Glaciers distinct from the Greenland and Antarctic ice sheets are shrinking rapidly, altering regional hydrology
, raising global sea level
and elevating natural hazards
. Yet, owing to the scarcity ...of constrained mass loss observations, glacier evolution during the satellite era is known only partially, as a geographic and temporal patchwork
. Here we reveal the accelerated, albeit contrasting, patterns of glacier mass loss during the early twenty-first century. Using largely untapped satellite archives, we chart surface elevation changes at a high spatiotemporal resolution over all of Earth's glaciers. We extensively validate our estimates against independent, high-precision measurements and present a globally complete and consistent estimate of glacier mass change. We show that during 2000-2019, glaciers lost a mass of 267 ± 16 gigatonnes per year, equivalent to 21 ± 3 per cent of the observed sea-level rise
. We identify a mass loss acceleration of 48 ± 16 gigatonnes per year per decade, explaining 6 to 19 per cent of the observed acceleration of sea-level rise. Particularly, thinning rates of glaciers outside ice sheet peripheries doubled over the past two decades. Glaciers currently lose more mass, and at similar or larger acceleration rates, than the Greenland or Antarctic ice sheets taken separately
. By uncovering the patterns of mass change in many regions, we find contrasting glacier fluctuations that agree with the decadal variability in precipitation and temperature. These include a North Atlantic anomaly of decelerated mass loss, a strongly accelerated loss from northwestern American glaciers, and the apparent end of the Karakoram anomaly of mass gain
. We anticipate our highly resolved estimates to advance the understanding of drivers that govern the distribution of glacier change, and to extend our capabilities of predicting these changes at all scales. Predictions robustly benchmarked against observations are critically needed to design adaptive policies for the local- and regional-scale management of water resources and cryospheric risks, as well as for the global-scale mitigation of sea-level rise.
Functional circuits are a group of combinational logic circuits which may be utilized for certain tasks and with specific planning. Decoders, multiplexers, and demultiplexers are all functional ...circuits that come in useful when creating complex systems. Quantum-dot cellular automata (QCA) is a flourishing technology that would be so practical in the field of computational digital circuits in terms of its advantages such as low energy consumption. This paper proposes various quaternary 1:4 decoders (enabling decoder, active-high and active-low decoders). Then, 4:1 multiplexer and 1:4 demultiplexer were architectured using the proposed 1:4 decoder. In the following, a quaternary to the binary converter (a 4-valued digit to a 2-bits circuit) is designed regarding the validated proposed structures. All designs were simulated and verified by QCASim. The total area used for the decoder, multiplexer, demultiplexer, and quaternary to the binary converter are 0.01, 0.19, 0.03, 0.13 μm
2
. The complexity and delay are 30, 387, 88, 214 and 0.5, 3.25, 1, 2 respectively. This work gets compared to CMOS and carbon nanotube field-effect transistor articles. Furthermore, the proposed 4:1 quaternary QCA multiplexer got compared with the binary QCA multiplexers. The comparison results show that our proposed designs are efficient in terms of having a low delay, area, and complexity.
The antibacterial effect of disinfectants is crucial for the control of Listeria monocytogenes in food processing environments. Tolerance of L. monocytogenes to sublethal levels of disinfectants ...based on quaternary ammonium compounds (QAC) is conferred by the resistance determinants qacH and bcrABC. The presence and distribution of these genes have been anticipated to have a role in the survival and growth of L. monocytogenes in food processing environments where QAC based disinfectants are in common use. In this study, a panel of 680 L. monocytogenes from nine Norwegian meat- and salmon processing plants were grouped into 36 MLVA profiles. The presence of qacH and bcrABC was determined in 101 isolates from the 26 most common MLVA profiles. Five MLVA profiles contained qacH and two contained bcrABC. Isolates with qacH and bcrABC showed increased tolerance to the QAC Benzalkonium chloride (BC), with minimal inhibitory concentrations (MICs) of 5–12, 10–13 and <5ppm for strains with qacH (two allele variants observed), bcrABC, and neither gene, respectively. Isolates with qacH or bcrABC were not more tolerant to BC in bactericidal tests in suspension or in biofilms compared with isolates lacking the genes. Water residue samples collected from surfaces in meat processing plants after QAC disinfection had bactericidal effect against L. monocytogenes when the sample BC levels were high (>100ppm). A sample with lower BC concentrations (14ppm of chain length C-12 and 2.7ppm of chain length C-14) inhibited growth of L. monocytogenes not containing bcrABC or qacH, compared to strains with these genes.
The study has shown that L. monocytogenes harbouring the QAC resistance genes qacH and bcrABC are prevalent in the food industry and that residuals of QAC may be present in concentrations after sanitation in the industry that result in a growth advantage for bacteria with such resistance genes.
•Tolerance of QAC disinfectants studied in L. monocytogenes from meat-and salmon processing•Efflux pumps genes qacH found in 22% and bcrABC in 8% of isolates•No protective effect of qacH or bcrABC in bactericidal tests with QAC•Residues of QAC found on surfaces after sanitation in meat processing plants•qacH and bcrABC gave growth advantage at concentrations of QAC present after sanitation.
Cationic biocides play a crucial role in the disinfection of domestic and healthcare surfaces. Due to the rise of bacterial resistance towards common cationic disinfectants like quaternary ammonium ...compounds (QACs), the development of novel actives is necessary for effective infection prevention and control. Toward this end, a series of 15 chimeric biscationic amphiphilic compounds, bearing both ammonium and phosphonium residues, were prepared to probe the structure and efficacy of mixed cationic ammonium-phosphonium structures. Compounds were obtained in two steps and good yields, with straightforward and chromatography-free purifications. Antibacterial activity evaluation of these compounds against a panel of seven bacterial strains, including two MRSA strains as well as opportunistic pathogen A. baumannii, were encouraging, as low micromolar inhibitory activity was observed for multiple structures. Alkyl chain length on the ammonium group was, as expected, a major determinant of bioactivity. In addition, high therapeutic indexes (up to 125-fold) for triphenyl phosphonium-bearing amphiphiles were observed when comparing antimicrobial activity to mammalian cell lysis activity.
Oxygen isotope records from Chinese caves characterize changes in both the Asian monsoon and global climate. Here, using our new speleothem data, we extend the Chinese record to cover the full ...uranium/thorium dating range, that is, the past 640,000 years. The record's length and temporal precision allow us to test the idea that insolation changes caused by the Earth's precession drove the terminations of each of the last seven ice ages as well as the millennia-long intervals of reduced monsoon rainfall associated with each of the terminations. On the basis of our record's timing, the terminations are separated by four or five precession cycles, supporting the idea that the '100,000-year' ice age cycle is an average of discrete numbers of precession cycles. Furthermore, the suborbital component of monsoon rainfall variability exhibits power in both the precession and obliquity bands, and is nearly in anti-phase with summer boreal insolation. These observations indicate that insolation, in part, sets the pace of the occurrence of millennial-scale events, including those associated with terminations and 'unfinished terminations'.
One of the concerns today's societies face is the development of resistant pathogenic microorganisms. The need to tackle this problem has driven the development of innovative antimicrobial materials ...capable of killing or inhibiting the growth of microorganisms. The present study investigates the dependence of the antimicrobial activity and solubility properties on the hydrophilicity/hydrophobicity ratio of antimicrobial coatings based on quaternary ammonium compounds. In this line, suitable hydrophilic and hydrophobic structural units were selected for synthesizing the antimicrobial copolymers poly(4-vinylbenzyl dimethyldodecylammonium chloride-co-acrylic acid), P(VBCDDA-co-AA20) and poly(dodecyltrimethylammonium 4-styrene sulfonate-co-glycidyl methacrylate), P(SSAmC
-co-GMA20), bearing an alkyl chain of 12 carbons either through covalent bonding or through electrostatic interaction. The cross-linking reaction of the carboxylic group of acrylic acid (AA) with the epoxide group of glycidyl methacrylate (GMA) of these two series of reactive antimicrobial copolymers was explored in blends, obtained through solution casting after curing at various temperatures. The release of the final products in pure water and NaCl 1 M solutions (as analyzed by gravimetry and total organic carbon, TOC/total nitrogen, TN analyses), could be controlled by the coating composition. The cross-linked polymeric membranes of composition 60/40
/
% ratios led to 97.8 and 99.7% mortality for
(
) and
(
), respectively, whereas the coating 20/80
/
% resulted in 96.6 and 99.8% cell reduction. Despite the decrease in hydrophobicity (from a 16- to a 12-carbon alkyl chain), the new materials maintained the killing efficacy, while at the same time resulting in increased release to the aqueous solution.
Dual-functional antifogging/antimicrobial polymer coatings were prepared by forming a semi-interpenetrating polymer network (SIPN) of partially quaternized poly(2-(dimethylamino)ethyl ...methacrylate-co-methyl methacrylate) and polymerized ethylene glycol dimethacrylate network. The excellent antifogging behavior of the smooth coating was mainly attributed to the hydrophilic/hydrophobic balance of the partially quaternized copolymer, while the covalently bonded, hydrophobic quaternary ammonium compound (5 mol % in the copolymer) rendered the coating strongly antimicrobial, as demonstrated by the total kill against both Gram-positive Staphylococcus epidermidis and Gram-negative Escherichia coli. The antimicrobial action of the SIPN coating was based on contact killing, without leaching of bactericidal species, as revealed by a zone-of-inhibition test. This type of dual-functional coating may find unique applications where both antimicrobial and antifogging properties are desired.
Quaternary ammonium compounds (QACs) are widely applied in household and industrial products. Most uses of QACs can be expected to lead to their release to wastewater treatment plants (WWTPs) and ...then dispersed into various environmental compartments through sewage effluent and sludge land application. Although QACs are considered to be aerobically biodegradable, the degradation is affected by its chemical structures, dissolved oxygen concentration, complexing with anionic surfactants, etc. High abundance of QACs has been detected in sediment and sludge samples due to its strong sorption and resistance to biodegradation under anoxic/anaerobic conditions. QACs are toxic to a lot of aquatic organisms including fish, daphnids, algae, rotifer and microorganisms employed in wastewater treatment systems. And antibiotic resistance has emerged in microorganisms due to excessive use of QACs in household and industrial applications. The occurrence of QACs in the environment is correlated with anthropogenic activities, such as wastewater discharge from WWTPs or single source polluters, and sludge land application. This article also reviews the analytical methods for determination of QACs in environmental compartments including surface water, wastewater, sewage sludge and sediments.
•QACs occur in the aquatic and terrestrial environment all over the world.•STPs are the main source of QACs released into environmental compartments.•QACs removal is dependent on sorption and biotransformation processes.•Excessive use of QACs results in the emergence of antibiotic-resistance bacteria.
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