Tat-induced lesions in transgenic mice do not correlate with the HIV-1 LTR transactivation

A pilot study was conducted in 7 normal volunteers to demonstrate the feasibility of employing pharmacokinetic tailoring to achieve matching plasma opioid concentration-time curves after epidural (e.p.) and intravenous (i.v.) alfentanil administration. Each subject participated in 1 pretest and 2 test sessions. Our pain model was cutaneous electrical stimulation of the finger and toe, adjusted to produce a baseline pain report of 5 (strong pain on a 0-5 scale). On test day 1, subjects received e.p. alfentanil (750 micrograms) and an i.v. saline infusion. Serial measurements of analgesia, end tidal CO2, pupil size, subjective side effects, and plasma alfentanil concentrations were conducted before and at various time intervals over a 4-h period after alfentanil administration. On test day 2, subjects received e.p. saline and a pharmacokinetically tailored i.v. infusion (using individual pharmacokinetics determined on the pretest day) designed to achieve a plasma concentration-time profile identical to that observed on the epidural day. The same battery of effect measurements was administered as on the 1st test day. Plasma alfentanil was measured to verify the accuracy of the tailored infusion. Plasma alfentanil concentration profiles were nearly identical on both test days. Peak plasma alfentanil concentrations were near the reported minimum effective analgesic concentration (MEAC). Overall, analgesia was slightly greater with e.p. administration. Onset of pain relief was rapid, and duration was approximately 1.5 h with e.p. and 1 h with i.v. alfentanil. There were no differences in pupil size, ETCO2, or subjective side effects between e.p. versus i.v. administration. We conclude that systemic redistribution from the epidural space appears to account for most, but not all, of the analgesia.     

The Use of Low-pressure Plasma on Enhancing the Attachment of Al2O3 Nanoparticles to Wood–Plastic Composites

Wood–plastic composites (WPC) are widely used for many purposes due to their interesting properties, but they have poor surface adhesion due to the chemical inertness of the matrix. Thus, in this work, the effect of plasma treatment on the WPC was investigated regarding its influence in the aluminum oxide (Al₂O₃) nanoparticles attachment to the surface. WPC were prepared in a polypropylene (PP) matrix, plasma-treated at 100 W for 600 s, and then covered with Al₂O₃ nanoparticles dispersion. The WPC/Al₂O₃ surfaces have been investigated by means of morphology, surface roughness, chemical structure, wettability, and nanohardness. Plasma treatment improved the attachment of Al₂O₃ onto WPC, which was confirmed by the higher presence of aluminum and oxygen-containing functional groups and the reduction of the intensity of peaks of methylene (CH₂) and methyl (CH₃) groups on the WPC surface. The higher surface reactivity of plasma-treated WPC resulted in a better distribution of the nanoparticles over the entire surface. In addition, plasma treatment avoided the formation of coffee-ring phenomenon but it was able to create cone-like structures on the WPC, increasing the surface roughness due to the etching effect and the attachment of Al₂O₃ nanoparticles. Plasma treatment followed by Al₂O₃ nanoparticles attachment increased the wettability, hardness, and elastic modulus of WPC at nanometric scale.     

Variability in nitrogen content of submerged aquatic vegetation: utility as an indicator of N dynamics within and among lakes

Submerged aquatic vegetation (SAV) may serve as an integrative proxy of spatial and temporal nitrogen (N) availability in aquatic ecosystems as plants are physiologically capable of storing variable amounts of N. However, it is important to understand whether plant species behave similarly or differently within and among systems. We sampled different SAV species along a nutrient gradient at multiple sites within several lakes to determine variability in C:N ratios and % N content among species, among plants of the same species at a single site, among sites and among lakes. Species respond differently suggesting that not all plant types can be used universally as nutrient proxies. The greatest variability in % N and C:N ratios for Valliseneria americana was observed among lakes whereas for Elodea canadensis it was among sites within a lake and among plants within a site. This suggests that V. americana could be a particularly useful indicator of N availability at larger spatial scales (regional and within a large fluvial lake) but that E. canadensis was not a particularly useful proxy.     

Formation of UHMWPE polymeric transfer films on sliding glass counterfaces: early and steady-state wear studied by transmission electron microscopy

At a temperature of 30°C polymeric transfer films were generated on glass counterfaces during small-amplitude oscillatory sliding contact with an ultra-high molecular weight polyethylene (UHMWPE) pin under a constant load of 6.5 MPa. Early discontinuous and continuous (steady-state) transfer films were studied with vertical platinum-carbon replication and transmission electron microscopy (TEM). Nanometre-scale UHMWPE deposits in these transfer films have been visualized for the first time. Nanometre-scale particles averaging 20.6 ±6.3nm (5–40nm) were deposited on glass in the early stages of UHMWPE film transfer. After formation of a continuous transfer film, UHMWPE particles of slightly smaller dimensions, 13.5±6.1 nm (2–41 nm), were deposited on the transfer film surface. In addition, micrometre-scale particles (0.1–6.4 m) were found at the ends of the wear track. At high magnification, a fraction of the UHMWPE polymer chains observed in particle surfaces and in the transfer film surface nearby were not oriented in the sliding direction. Some crystal- or plate-like particles of UHMWPE were seen in the transfer film. Plate-like and micrometre-scale spherulitic inclusions were also identified on the mostly amorphous UHMWPE pin surface fractured at liquid nitrogen temperatures. The high frequency of nanometre-scale UHMWPE particles in contrast to the less numerous micrometre-scale deposits near the ends of the wear track suggests that the nanometre-scale deposits contribute significantly to transfer film formation and to the wear characteristics of UHMWPE.To whom correspondence should be addressed.     

Origin of the Static Fatigue Limit in Oxide Glasses

Oxide glasses exhibit slow crack growth under stress intensities below the fracture toughness in the presence of water vapor or liquid water. The log of crack velocity decreases linearly with decreasing stress intensity factor in Region I. For some glasses, at a lower stress intensity, K_o, log v asymptotically diminishes where there is no measurable crack growth. The same glasses exhibit static fatigue, or a decreasing strength for increasing static loading times, as cracks grow and stress intensity eventually reaches the fracture toughness. In this case, some glasses exhibit a low stress below which no fatigue/failure is observed. The absence of slow crack growth under a low stress intensity factor is called the fatigue limit. Currently, no satisfactory explanation exists for the origin of the fatigue limit. We show that the surface stress relaxation mechanism, which is promoted by molecular water diffusion near the glass surface, may be the origin of the fatigue limit. First, we hypothesize that the slowing down of slow crack growth takes place due to surface stress relaxation during slow crack growth near the static fatigue limit. The applied stress intensity becomes diminished by a shielding stress intensity due to relaxation of crack tip stresses, thus resulting in a reduced crack velocity. This diminishing stress intensity factor should result in a crack growth rate near the static fatigue limit that decreases in time. By performing Double Cantilever Beam crack growth measurements of a soda‐lime silicate glass, a decreasing crack growth rate was measured. These experimental observations indicate that surface stress relaxation is causing crack velocities to asymptotically become immeasurably small at the static fatigue limit. Since the surface stress relaxation was shown to take place for various oxide glasses, the mechanism for fatigue limit explained here should be applicable to various oxide glasses.     

Exposure to toxic metals and persistent organic pollutants in Inuit children attending childcare centers in Nunavik, Canada

Arctic populations are exposed to substantial levels of environmental contaminants that can negatively affect children's health and development. Moreover, emerging contaminants have never been assessed in Inuit children. In this study, we document the biological exposure to toxic metals and legacy and emerging persistent organic pollutants (POPs) of 155 Inuit children (mean age 25.2 months) attending childcare centers in Nunavik. Blood samples were analyzed to determine concentrations of mercury, lead, polychlorinated biphenyls (PCBs), pesticides, brominated flame retardants [e.g., polybrominated diphenyl ethers (PBDEs)] and perfluoroalkyl and polyfluoroalkyl substances [PFASs; e.g. perfluorooctanesulfonate (PFOS) and perfluorooctane (PFOA)]. Lead [geometric mean (GM) 0.08 μmol/L], PCB-153 (GM 22.2 ng/g of lipid), BDE-47 (GM 184 ng/g of lipid), PFOS (GM 3369 ng/L), and PFOA (GM 1617 ng/L) were detected in all samples. Mercury (GM 9.8 nmol/L) was detected in nearly all blood samples (97%). Levels of metals and legacy POPs are consistent with the decreasing trend observed in Nunavik and in the Arctic. PBDE levels were higher than those observed in many children and adolescents around the world but lower than those reported in some U.S. cities. PFOS were present in lower concentrations than in Nunavimmiut adults. There is a clear need for continued biomonitoring of blood contaminant levels in this population, particularly for PBDEs and PFASs.     

Determinants of diet quality among rural households in an intervention zone of Grande Anse,Haiti

In Haiti, nutrient deficiencies and stunting are major public health concerns. These health problems are caused by poor access and consumption of nutrient-rich foods, among other factors. The aim of this study was to assess the diet quality of rural Haitian households and identify its socioeconomic determinants. In August–September 2012, female caregivers from 529 rural households from the Department of Grande Anse participated in a cross-sectional survey. Collected data included household food production activities and socioeconomic characteristics. Diet quality was assessed using the Household Dietary Diversity Score. Its determinants were identified using multiple linear regression analyses. Results revealed that many households consumed oil/fats, condiments/beverages/spices, roots/tubers, and cereals, whereas few households consumed animal-based foods such as meats/organs, dairy products and eggs. Among household-level determinants, the number of adults per household, land ownership, practice of livestock rearing, number of meals consumed by children, use of latrines and accessibility of the dwelling location perceived as difficult were all associated with higher household dietary diversity. Among individual-level variables, respondent participation in petty commerce and practice of agriculture as main occupation, in addition to increased level of education were positively associated with household dietary diversity. In sum, determinants of diet quality were multidimensional and were associated with various factors including socio-economic status, household demographics, and physical environment. Moreover, diet quality is concurrently linked with household- and individual-level determinants. This highlights the need for multisectoral and multilevel interventions to improve household diet quality in Haiti.     

Control of lubricant transport by a CrN diffusion barrier layer during high-temperature sliding of a CrN-Ag composite coating

CrN-Ag composite coatings, 2 and 5 μm thick and containing 22 at.% Ag solid lubricant, were grown on Si(001) and 440C stainless steel substrates by reactive co-sputtering at T_s = 500 °C, and were covered with 200 nm thick pure CrN diffusion barrier cap layers. Annealing experiments at T_a = 625 °C, followed by quantitative scanning electron microscopy, energy dispersive x-ray spectroscopy, and Auger depth profile analyses indicate considerable Ag transport to the top surface for a barrier layer deposited at a substrate floating potential of −30 V, but negligible Ag diffusion when deposited with a substrate bias potential of −150 V. This is attributed to ion-irradiation induced densification which makes the cap layer an effective diffusion barrier. High temperature tribological sliding tests of this coating system against alumina balls at T_t = 550 °C indicate an initial friction coefficient μ = 0.43 ± 0.04 which decreases monotonically to 0.23 ± 0.03. This is attributed to the development of wear mediated openings in the barrier layer which allow Ag lubricant to diffuse to the sliding top surface. In contrast, pure CrN exhibits a constant μ = 0.41 ± 0.02 while CrN-Ag composite coatings without cap layer show a low transient μ = 0.16 ± 0.03, attributed to Ag transport to the surface, that however increases to μ = 0.39 ± 0.04 after ~ 6000 cycles as the Ag reservoir in the coating is depleted. That is, the dense CrN cap layer reduces the Ag lubricant flow rate and therefore prolongs the time when the coating provides effective lubrication. This results in a cumulative wear rate over 10,000 cycles of 3.1 × 10⁻⁶ mm³/Nm, which is 3.3 × lower than without diffusion barrier layer.     

Suppression of wear in graphene polymer composites

Polytetrafluoroethylene (PTFE) is one of the most widely used solid lubricants but suffers from a high wear rate which limits its applications. Here we report four orders of magnitude reduction in the steady state wear rate of PTFE due to graphene additives. The wear rate of unfilled PTFE was measured to be ～0.4 × 10^?3 mm³/N m which is reduced to ～10^?7 mm³/N m by the incorporation of 10 wt% of graphene platelets. We also performed a head-to-head comparison of wear rate with graphene and micro-graphite fillers at the same weight fractions. In general, we find that graphene fillers gave 10–30 times lower wear rates than micro-graphite at the same loading fraction. Scanning electron microscopy analysis indicated noticeably smaller wear debris size in the case of graphene/PTFE composites indicating that graphene additives are highly effective in regulating debris formation in PTFE leading to reduced wear.