EELS study of niobium carbo-nitride nano-precipitates in ferrite

Micro-alloying steels allow higher strength to be achieved, with lower carbon contents, without a loss in toughness, weldability or formability through the generation of a fine ferrite grain size with additional strengthening being provided by the fine scale precipitation of complex carbo-nitride particles. Niobium is reported to be the most efficient micro-alloying element to achieve refinement of the final grain structure. A detailed microscopic investigation is one of the keys for understanding the first stages of the precipitation sequence, thus transmission electron microscopy (TEM) is required. Model Fe-(Nb,C) and Fe-(Nb,C,N) ferritic alloys have been studied after annealing under isothermal conditions. However the nanometre scale dimensions of the particles makes their detection, structural and chemical characterization delicate. Various imaging techniques have then been employed. Conventional TEM (CTEM) and high resolution TEM (HRTEM) were used to characterise the morphology, nature and repartition of precipitates. Volume fractions and a statistical approach to particle size distributions of precipitates have been investigated by energy filtered TEM (EFTEM) and high angle annular dark field (HAADF) imaging. Great attention was paid to the chemical analysis of precipitates; their composition has been quantified by electron energy loss spectroscopy (EELS), on the basis of calibrated 'jump-ratios' of C-K and N-K edges over the Nb-M edge, using standards of well-defined compositions. It is shown that a significant addition of nitrogen in the alloy leads to a complex precipitation sequence, with the co-existence of two populations of particles: pure nitrides and homogeneous carbo-nitrides respectively.

Mechanisms of PhotoBioModulation (PBM) focused on oral mucositis prevention and treatment: a scoping review

BACKGROUND

Oral mucositis (OM) is a severe complication cancer patients undergo when treated with chemoradiotherapy. Photobiomodulation (PBM) therapy also known as low-level laser therapy has been increasingly used for the treatment of such oral toxicity. The aim of this review is to discuss the mechanisms of photobiomodulation (PBM) regarding OM prevention and treatment, and more precisely to focus on the effect of PBM on tumor and healthy cells.

METHODS

MEDLINE/PubMed, and google scholar were searched electronically. Selected studies were focusing on PBM effects on tumor and healthy cells.

RESULTS

PBM interactions with the tissue and additional mechanism in OM therapy were detailed in this review. Moreover, this review highlighted a controversy about the carcinogenic effect of PBM. Indeed, Many studies reported that PBM could enhance malignant cell proliferation; suggesting that PBM would have no protective effect. In addition to acting on cancer cells, PBM may damage healthy cells.

CONCLUSION

More prospective studies are needed to assess the effect of PBM on cancer cells in order to improve its use for OM prevention and treatment.

[Sedation and analgesia practices among Spanish neonatal intensive care units]

INTRODUCTION

Pain management and sedation is a priority in neonatal intensive care units. A study was designed with the aim of determining current clinical practice as regards sedation and analgesia in neonatal intensive care units in Spain, as well as to identify factors associated with the use of sedative and analgesic drugs.

METHOD

A multicenter, observational, longitudinal and prospective study.

RESULTS

Thirty neonatal units participated and included 468 neonates. Of these, 198 (42,3%) received sedatives or analgesics. A total of 19 different drugs were used during the study period, and the most used was fentanyl. Only fentanyl, midazolam, morphine and paracetamol were used in at least 20% of the neonates who received sedatives and/or analgesics. In infusions, 14 different drug prescriptions were used, with the most frequent being fentanyl and the combination of fentanyl and midazolam. The variables associated with receiving sedation and/or analgesia were, to have required invasive ventilation (P<.001; OR=23.79), a CRIB score >3 (P=.023; OR=2.26), the existence of pain evaluation guides in the unit (P<.001; OR=3.82), and a pain leader (P=.034; OR=2.35).

CONCLUSIONS

Almost half of the neonates admitted to intensive care units receive sedatives or analgesics. There is significant variation between Spanish neonatal units as regards sedation and analgesia prescribing. Our results provide evidence on the "state of the art", and could serve as the basis of preparing clinical practice guidelines at a national level.

Regulation of nitrogen fixation from free-living organisms in soil and leaf litter of two tropical forests of the Guiana shield

BACKGROUND AND AIMS

Biological fixation of atmospheric nitrogen (N₂) is the main pathway for introducing N into unmanaged ecosystems. While recent estimates suggest that free-living N fixation (FLNF) accounts for the majority of N fixed in mature tropical forests, the controls governing this process are not completely understood. The aim of this study was to quantify FLNF rates and determine its drivers in two tropical pristine forests of French Guiana.

METHODS

We used the acetylene reduction assay to measure FLNF rates at two sites, in two seasons and along three topographical positions, and used regression analyses to identify which edaphic explanatory variables, including carbon (C), nitrogen (N), phosphorus (P) and molybdenum (Mo) content, pH, water and available N and P, explained most of the variation in FLNF rates.

RESULTS

Overall, FLNF rates were lower than measured in tropical systems elsewhere. In soils seasonal variability was small and FLNF rates differed among topographies at only one site. Water, P and pH explained 24% of the variation. In leaf litter, FLNF rates differed seasonally, without site or topographical differences. Water, C, N and P explained 46% of the observed variation. We found no regulatory role of Mo at our sites.

CONCLUSIONS

Rates of FLNF were low in primary rainforest on poor soils on the Guiana shield. Water was the most important rate-regulating factor and FLNF increased with increasing P, but decreased with increasing N. Our results support the general assumption that N fixation in tropical lowland forests is limited by P availability.

Ethylene spectroscopy using a quasi-room-temperature quantum cascade laser

Spectroscopic measurements on ethylene were performed using a quasi-room-temperature quantum cascade (QC) laser operated in pulsed mode in the 10.3 microm range. Using transmission spectroscopy, a broadening of the ethylene absorption spectrum was observed with increasing laser pulse duration, due to an increase of the laser linewidth. This linewidth was determined from the measured absorption spectra, showing a value of 0.04 cm(-1) for a 20 ns pulse duration and an enhancement coefficient of 6.5 x 10(-3) cm(-1) per ns in the 20-50 ns pulse length range. Photoacoustic (PA) detection of ethylene was also performed using the QC laser and a resonant PA cell, with a detection limit of 60 ppm.

Photobiomodulation by a new optical fiber device: analysis of the in vitro impact on proliferation/migration of keratinocytes and squamous cell carcinomas cells stressed by X-rays

Photobiomodulation-based (PBM-based) therapies show promising results in mucositis and dermatitis treatment by stimulating wound healing mechanisms such as cell proliferation and migration. The aim of the present study is to investigate the in vitro effects of CareMin650 on the proliferation and migration of two different types of cells, namely cancer and non-cancer cells, with or without X-ray radiation. Study design used PBM through a combination of 0-3-6 J/cm² doses-with or without X-ray radiation-on the proliferation and migration capabilities of a keratinocyte cell line (HaCaT) and a squamous cell carcinoma line (SCC61). PBM is delivered by a new woven optical fiber device, namely CareMin650 prototype (light emission by LEDs (light-emitting diodes), peak at 660 nm, irradiance of 21.6 mW/cm²). The effectiveness of PBM to increase HaCaT proliferation and migration (with or without X-ray radiation) supports the capability of PBM to favor wound healing. It also highlights that PBM does not provide any anti-radiation effect to previously X-rays radiated SCC (p < 0.001). Such data supports the beneficial effect of PBM delivered by an optical fiber device to heal wounds, without promoting cancer development.

[Impact of hospitalization of an infant during breast-feeding: mother-child investigation]

A real health priority for governments, breastfeeding has prompted WHO and UNICEF to create the "Baby-Friendly Hospital Initiative" for maternity units respecting the "ten steps to successful breastfeeding". This effort does not include pediatric departments. However, as the properties of breast milk enhance recovery of the infant, it is also important to promote breastfeeding in this branch. Furthermore, few studies have analyzed the constraints of hospitalization on the breastfeeding process. The aim of this study is to identify the constraints imposed by hospitalization on the process of breastfeeding in infants aged 29 days to 6 months suffering from acute disease, during hospitalization and within a week following their return home. This prospective study was conducted between October 1st and December 31st, 2008 in a pediatric department through interviews and questionnaires from breastfeeding mothers and health professionals. 51 mother-infant pairs and 35 caregivers were included in the study. During hospitalization; direct breastfeeding was interrupted for 31 mothers. After hospitalization, 3 mothers had weaned their babies, 12 went from exclusive breastfeeding to mixed feeding and 13 had experienced difficulties. Caregivers partially meet WHO's recommendations. The hospitalization of an infant disrupts the continuation of breastfeeding. To overcome this, actions must be taken in relation with hospitals, departments and professionals. The study's small sample does not prove that the original training of caregivers influence theirs practices.

Contrasting nitrogen and phosphorus fertilization effects on soil terpene exchanges in a tropical forest

Production, emission, and absorption of biogenic volatile organic compounds (BVOCs) in ecosystem soils and associated impacts of nutrient availability are unclear; thus, predictions of effects of global change on source-sink dynamic under increased atmospheric N deposition and nutrition imbalances are limited. Here, we report the dynamics of soil BVOCs under field conditions from two undisturbed tropical rainforests from French Guiana. We analyzed effects of experimental soil applications of nitrogen (N), phosphorus (P), and N + P on soil BVOC exchanges (in particular of total terpenes, monoterpenes, and sesquiterpenes), to determine source and sink dynamics between seasons (dry and wet) and elevations (upper and lower elevations corresponding to top of the hills (30 m high) and bottom of the valley). We identified 45 soil terpenoids compounds emitted to the atmosphere, comprising 26 monoterpenes and 19 sesquiterpenes; of these, it was possible to identify 13 and 7 compounds, respectively. Under ambient conditions, soils acted as sinks of these BVOCs, with greatest soil uptake recorded for sesquiterpenes at upper elevations during the wet season (-282 μg m^-2 h^-1). Fertilization shifted soils from a sink to source, with greatest levels of terpene emissions recorded at upper elevations during the wet season, following the addition of N (monoterpenes: 406 μg m^-2 h^-1) and P (sesquiterpenes: 210 μg m^-2 h^-1). Total soil terpene emission rates were negatively correlated with total atmospheric terpene concentrations. These results indicate likely shifts in tropical soils from sink to source of atmospheric terpenes under projected increases in N deposition under global change, with potential impacts on regional-scale atmospheric chemistry balance and ecosystem function.