AM Samples Research Articles

The use of compact specimens to determine fracture toughness anisotropy of Ti–6Al–4V additively manufactured for repair

The use of compact specimens to determine the fracture toughness anisotropy of Ti–6Al–4V additively manufactured for repair by directed energy deposition (DED) technique via thin was thoroughly investigated by microstructure examination and fracture toughness test. One characteristic of DED is the anisotropy of the microstructure due to local heating and the build direction. The specimens were originally part of an additively manufactured repair study where AM material was added to an already existing mild heat treated wrought Ti–6Al–4V bar. To understand the intrinsic anisotropy of fracture toughness in the AM build, small size specimens were machined from the halved AM and wrought Ti of the repaired specimens. The crack mouth opening displacements were measured using digital image correlation (DIC). The mechanical testing was supported with direct current potential drop (DCPD) to monitor the formation and growth of cracks. To gain insights into failure mechanisms and microscopic characteristics, polished sections and fractured surfaces were examined. The measured fracture toughness of DED AM samples were compared with wrought annealed Ti–6Al–4V in relations to the microstructure features. Hence, the fracture toughness of the DED specimens depended on orientation with the orientation of the notch perpendicular to the build layer possessing higher fracture toughness. The fracture toughness of DED AM specimens with the notch configuration perpendicular to the build layers were found slightly higher than the wrought Ti–6Al–4V, respectively.

Serum exosomal microRNAs as predictive markers for EGFR mutations in non-small-cell lung cancer.

BackgroundCurrent therapeutic drugs show positive effects on non–small‐cell lung cancer (NSCLC) patients with mutant epidermal growth factor receptor (EGFR) expression, whereas a lesser beneficial effect is generally noted on NSCLC patients with wild‐type EGFR. Therefore, identification of new detection methods for the accurate clinical diagnosis of NSCLC is essential.MethodsIn this study, tumor‐derived exosomes from the plasma of EGFR mutation and wild‐type NSCLC patients were isolated. Extensive exosomal miRNA profiling of EGFR mutation and wild‐type NSCLC patients, in comparison with healthy individuals, was performed using miRNA‐sequencing analysis.ResultsThe variation of exosomal miRNA expression between control group (NR) and NCSLC samples (AM and AW) was identified. 96 significantly different expressed miRNAs were identified. Of these, 39 miRNAs were upregulated and 57 were downregulated. 11 miRNAs were downregulated, and 31 miRNAs were upregulated in the miRNA expression between NR and AM. Compared with healthy donors, 54 upregulated miRNAs and 36 downregulated miRNAs were observed in samples from AW patients. 40 different expressed miRNAs were identified in AM samples, compared with AW. Ten of upregulated miRNAs are miR‐260, miR‐1169, miR‐117, miR‐15b‐5p, miRNA‐731, miR‐342‐5p, miR‐ 898, miR‐1384, miR‐56, and miR‐1214. Ten of downregulated miRNAs are miR‐99b‐5p, miR‐1116, miR‐689, miR‐818, miR‐604, miR‐72, miR‐955, miR‐403, miR‐1228, and miR‐836.ConclusionThe exosomal miR‐1169 and miR‐260 as potential candidates, which contain specific characteristics that can distinguish between wild‐type EGFR and mutant EGFR NSCLC patients in early‐stage cancers.

In Situ Anchoring Ultra Small Au Nanoparticles by Conformal Coating of Carbon Layer within the Micro-Environments of Mesoporous Silica for Highly Efficient Catalytic Reduction of 4-nitrophenol

For the noble-metal based catalysts, the metal dispersion and sinter resistance of the metal nanoparticles (NPs) are the most vital factors for their application in series catalytic reactions. However, in the most noble-metal based catalysts, the weak interaction between metal NPs and support would be negative for these factors, and the poor catalytic performance would be obtained relatively. Committed to overcome these, in this work, the catalyst of Au@C/AMS would be designed and fabricated by the hydrothermal and calcinations process, in which the ultra small Au NPs are formed and stabilized in situ by the conformal coating of carbon layer in the micro-environment of mesoporous silica. The results demonstrate that the carbon layer would be directly formed in the mesoporous channels by calcinations in nitrogen atmosphere, and the ultra small Au NPs would be in situ anchored in the carbon layer. The average particle size of Au in Au@C/AMS is as small as 1.8 nm from TEM results, which is much smaller than those in the sample of Au/AMS without the protection of carbon layer. Besides, compared with the samples that the Au NPs are deposited on the outer and inner surface of mesoporous silica, a strong interaction would be built between Au NPs and support in the target Au@C/AMS sample. As expected, the catalyst of Au@C/AMS displays superior catalytic activity and stability in the liquid-phase reduction of 4-nitrophenol. The construction of this special architecture for Au-based catalysts could provide new sights for the design and fabrication of noble metal-based mesoporous materials with desirable catalytic activity and stability. In this work, the catalyst of Au@C/AMS would be designed and fabricated by the hydrothermal and calcinations process, in which the ultra small Au NPs are formed and stabilized in situ by the conformal coating of carbon layer in the micro-environment of mesoporous silica. Compared with the samples that the Au NPs are deposited on the outer and inner surface of mesoporous silica, a strong interaction would be built between Au NPs and support in the target Au@C/AMS sample. As expected, the catalyst of Au@C/AMS displays superior catalytic activity and stability in the liquid-phase reduction of 4-nitrophenol. The construction of this special architecture for Au-based catalysts could provide new sights for the design and fabrication of noble metal-based mesoporous materials with desirable catalytic activity and stability.

Juvenile Children’s Salivary Aldosterone and Cortisone Decrease during Informal Math and Table-Tennis Competitions

Among adults, aldosterone and cortisone increases are reported in response to physically taxing forms of competition, enabling individuals to rapidly adapt to variable sociocompetitive contexts. Yet, aldosterone and cortisone responses in juvenile children engaged in less strenuous forms of competition have not been investigated. Here, we sought to measure aldosterone and cortisone responses in children who participated in math and table-tennis competitions. We hypothesized that the responses would significantly vary with respect to the type of competition. Pre- and post-match salivary aldosterone and cortisone were measured in Hong Kongese children, aged 8–11 years, during (1) a mixed-sex, team-based, math competition (N = 45) and (2) a dyadic, table-tennis competition against peers (N = 22). In the math competition, aldosterone and cortisone levels decreased in boys and girls, while members on losing teams had greater match decreases in cortisone levels compared to individuals on winning teams. In the table-tennis competition, time of day led to significant diurnal differences in competitors’ pre-match aldosterone and cortisone concentrations. As a result, each sample was analyzed independently according to match time (8:30 AM and 11:00 AM). Aldosterone levels decreased among the competitors who participated in the 11:00 AM table-tennis matches. Cortisone levels decreased for the majority of competitors, but only significantly decreased in the 8:30 AM sample. These findings highlight that juvenile competitors’ hypothalamic-pituitary-adrenal (HPA) axis and renin-angiotensin-aldosterone system (RAAS) are sensitive to less physically strenuous forms of competition. Further, the differences in the competitive environment likely stimulate the direction of aldosterone (RAAS) and cortisone (HPA) reactive change.

Mechanical properties and corrosion resistance of cobalt-chrome alloy fabricated using additive manufacturing

Recent progress in metal additive manufacturing methods allowed fabrication of parts with complex geometry while attaining comparable or superior to parts fabricated using conventional methods. Considering its efficient use of material, potential for light-weighing and role in closing the digital to physical gap, additive manufacturing emerged as a promising technology. In AM, the commonly used methods are selective laser melting (SLM) and Electron Beam Melting (EBM). Cobalt Chrome (CoCr) is gaining popularity as a biomaterial parts produced via AM. In this study, mechanical and corrosion properties of additively manufactured CoCr alloy are investigated and compared to those of the same alloy produced via casting. Samples produced using AM (SLM & EBM) and casting are compared in terms of mechanical properties (tensile strength, yield strength & hardness) and corrosion resistance. The microstructures were observed using SEM and corrosion resistance were tested using EIS. The mechanical properties of SLM printed parts are found to be more superior than cast produced part due to the smaller grain size of SLM printed parts. The grain size for SLM printed part is 30 µm while for cast is 4000 µm. For yield strength, the values were 840 MPa and 730 MPa for both SLM & EBM as-built samples while for cast sample was at 450 MPa. The yield strength values decreased to 622 MPa and 560 MPa for both SLM & EBM respectively post HIP-ing. For tensile strength, the values were 1070 MPa and 960 MPa for both SLM & EBM respectively while for cast samples, the value was at 655 MPa. As for hardness values (HRC), they were at 38 and 47 for both SLM & EBM respectively while for cast samples, the value was at 30. Post HIP-ing, hardness values (HRC) decreased to 36 and 34 respectively. Meanwhile, the corrosion resistance, Rct value for AM sample is at 6.21 ± 3.91 MU cm−2 while for cast sample is at 3.74 ± 1.86 MU cm−2. In conclusion, AM produced parts fare better than conventional cast part in terms of mechanical properties (tensile strength, yield strength & hardness) and corrosion resistance.

Mechanical behavior of additive manufactured AISI 420 martensitic stainless steel

This study investigates the mechanical behavior of laser-cladded and additively manufactured AISI 420 martensitic stainless steel (MSS) in the longitudinal and transverse direction. Microstructural features were characterized using scanning electron microscopy (SEM) and electron back-scattered diffraction (EBSD) techniques. EBSD analysis was also used to measure the grain size and volume fraction and distribution of each phase present. The mechanical testing results revealed anisotropic mechanical properties in both longitudinal and transverse directions. To address the anisotropic issue, post-cladding heat treatment was proposed. It was shown that the post-cladding one-hour heat treatment at 565 °C effectively eliminated the anisotropic behavior of the laser-cladded 420 stainless steel. Furthermore, as an alternative solution, cross-layered as well as angular powder deposition were studied. The AM sample built at angular powder deposition (30°) against the horizontal base improved the mechanical properties and minimized the directionality challenges.

Serum oxidative stress influences neurological recovery after surgery to treat acutely worsening symptoms of compression myelopathy: a cross-sectional human study

BackgroundRecent reports indicate that oxidative stress induced by reactive oxygen species is associated with the pathobiology of neurodegenerative disorders that involve neuronal cell apoptosis. Here we conducted a cross-sectional study to evaluate serum levels of oxidative stress in cervical compression myelopathy.MethodsThirty-six serum samples were collected preoperatively from patients treated for acutely worsening compression myelopathy (AM) and chronic compression myelopathy (CM). Serum levels of oxidative stress markers were evaluated by measuring derivatives of reactive oxygen metabolites (ROM), which reflect concentrations of hydroperoxides. ROM in healthy individuals range from 250 to 300 (U. CARR), whereas ROM >340–400 and > 400 define moderate and severe levels of oxidative stress, respectively. Difference of ROM by the cause of disorders whether cervical spondylotic myelopathy (CSM) or cervical ossification of longitudinal ligament (OPLL), correlations between ROM and patient age, body mass index (BMI), history of smoking, existence of diabetes were examined. Neurological evaluations according to Japanese Orthopaedic Association (JOA) scores were performed and correlated with ROM.ResultsROM increased to 349.5 ± 54.8, representing a moderate oxidative stress, in CM samples. ROM increased to 409.2 ± 77.9 in AM samples, reflecting severe oxidative stress which were significantly higher than for CM samples (p < 0.05). There was no significant difference by the cause of disorders (CSM or OPLL). ROM were significantly increased in AM serum samples from female patients versus AM male and CM patients (p < 0.05). There were no correlations between ROM and age, BMI, history of smoking, and existence of diabetes. A negative correlation between ROM and recovery rate of JOA score (R2 = 0.454, p = 0.047) was observed in the AM group.ConclusionsAlthough moderate oxidative stress was present in patients with CM, levels of oxidative stress increased in severity in patients with AM. These results suggest that postsurgical neurological recovery is influenced by severe oxidative stress in AM.

Variation in the microbial community contributes to the improvement of the main active compounds of Magnolia officinalis Rehd. et Wils in the process of sweating

BackgroundMagnolia officinalis Rehd. et Wils, commonly called Houpo, has been used for thousands of years in China as a traditional herbal medicine. The primary processing of Houpo requires sweating treatment, which is a special drying process and is considered to be an essential embodiment of high quality and genuine medicinal materials. The sweating of Houpo leads to peculiar changes in the microbial community structure and the content of main active substances (magnolol, honokiol, syringin and magnoflorine). Variation in the microbial community was considered the cause of the change in content of active substances of Houpo, although the microbial taxa responsible for the improvement of content remain unidentified.MethodsIn this study, we used MiSeq high-throughput sequencing methods for partial bacterial 16S rRNA and 18S rRNA gene sequences to compare the bacterial and fungal community structures at different timepoints in the process of sweating. The content of the main active substances (magnolol, honokiol, syringin and magnoflorine) were determined by high-performance liquid chromatography analysis to evaluate the effects of sweating. UPLC-Q-Extractive Orbitrap mass spectrometry (UPLC-QE Orbitrap MS) was used to detection of differential metabolites of unsweated Houpo before and after co-culture with core bacterial solutions.ResultsIn this study, the total contents of magnolol (MG) and honokiol (HK) were significantly increased at 4 dp (dp for day PM sample), up to 3.75%, and the contents of syringin (SG) and magnoflorine (MF) were as high as 0.12% and 0.06%, respectively. Bacterial abundance and diversity were higher in the early stage (0 day–2 da; da for day AM sample) than in the later stage (4–5 dp), while fungal abundance was more obvious in the later stage than in the early stage. Positive correlation coefficients revealed that the relative abundance of Enterobacter (P < 0.05), Klebsiella (P < 0.05), Weissella (P < 0.05), Bacillus (P < 0.05) and Candida (P < 0.05) would be conducive to improving the quality of Houpo. Negative correlation coefficients revealed that the relative abundance of Actinomycetospora, Singulisphaera, Mucilaginibacter, Deinococcus, Gemmatirosa, Methylobacterium, Sphingomonas, Hymenobacter, Halomonas and Capnobotryella could be a potential antagonist for the decrease in the quality of Houpo. After co-culture of single core strain and unsweated Houpo, there was no significant difference in the four main active components, but there were other metabolites with significant difference.ConclusionsOur findings reveal that sweating increased the content of the main active compounds, promoted the relative abundance of potentially beneficial microbes, decreased the abundance of potentially harmful microbes, the core functional genera group together, forming a core microbiome, these genera are dominant across the different stages of the sweating process and contribute to the quality development of the characteristics of Houpo. Meanwhile, this study presented a clear scope for potential beneficial microbes that improve the quality of Houpo.

Additively manufactured 316L stainless steel: An efficient electrocatalyst

In the quest of finding an economical, yet efficient material, the idea of fabricating 316L stainless steel using additive manufacturing technology was explored to produce material with refined sub-granular structure. The surface of the stainless steel was further chemically treated with an etching solution to expose the grain boundaries. The grain boundary enriched surface resulted in more active sites for the oxygen evolution reaction (OER) in additively manufactured treated (AM-T) 316L stainless steel. AM-T sample manifests enhanced catalytic activity for OER with an overpotential of 310 mV to draw a 10 mA/cm2 current density, along with a lower Tafel slope of 42 mV/dec compared to AM and wrought samples. These features were validated from the increased double-layer capacitance of AM-T and approximately 1.5 times larger electrochemically effective surface area of AM-T due to etching treatment compared to the wrought sample. Furthermore, AM-T also possesses stable activity retention for 100 h at a current density of 10 mA/cm2.

36Cl preparation method for Chinese Karst samples (Tiankeng)

Tiankeng, a typical Karst relief of the Late Quaternary Period, in the south of China, plays an important role when researching the surface shape and evolution of the Karst relief. The accumulation of Chlorine-36 (T1/2 = 301 ka) through the interaction of cosmic ray particles with Ca, K and Cl in rocks allow it to be used as the ideal nuclide for determination of the exposure age and erosion rate of limestone. In this work, an improved 36Cl sample preparation method for Tiankeng limestone was presented. The Isotope Dilution-AMS technique allows for the simultaneous measurement of 36Cl and Cl with a single AMS sample preparation. The barium introduced during the sample preparation was removed to avoid ionizer poisoning and attain a higher and more stable beam current. The method is particularly suitable for limestone samples, as well as for soil, sediment and water samples.

Antioxidant, Cytotoxicity, and Antiophidian Potential of Alstonia macrophylla Bark.

The objective of this research was to find the possible pharmacognosy of the bark of the Philippine Alstonia macrophylla Wall. ex G.Don (AM). Gas chromatographic–mass spectral (GC–EI-MS) characterization and energy dispersive X-ray spectroscopy (EDX) were performed to detect the bioactive constituents. EDX analysis of AM bark displayed a high content of potassium (3.26%) and calcium (2.96%). Eight constituents were detected in AM crude dichloromethane (DCM) extracts, which consisted of a long-chain unsaturated fatty acid (17:0) and fatty acid esters such as ethyl hexadecanoate and methyl hexadecanoate. Extraction of AM bark using methanol and dimethyl sulfoxide (MeOH/DMSO) solvents resulted in the identification of 17 constituents, principally alkaloids (alstonerine, 34.38%; strictamin, 5.23%; rauvomitin, 4.29%; and brucine, 3.66%) and triterpenoids (γ-sitosterol, 3.85%; lupeol, 3.00%; 24-methylenecycloartanol, 2.81%; campesterol, 2.71%; β-amyrin, 2.30%; and stigmasterol, 2.13%). MeOH/DMSO samples of AM were used in the selected bioassays. The samples exhibited efficient free radical scavenging activity (IC50 = 0.71 mg/mL) and were noncytotoxic to normal HDFn (IC50 > 100 μg/mL) and neoplastic THP-1 cell lines (IC50 = 67.22 μg/mL) while highly degenerative to MCF-7 (IC50 = 6.34 μg/mL), H69PR (IC50 = 7.05 μg/mL), and HT-29 (IC50 = 9.10 μg/mL). Most interestingly, the AM samples inhibited the northern Philippine Cobra’s (Naja philippinensis Taylor) venom (IC50 = 297.27 ± 9.33 μg/mL) through a secretory phospholipase A2 assay.

Nanoindentation based properties of Inconel 718 at elevated temperatures: A comparison of conventional versus additively manufactured samples

In this work, temperature dependent mechanical properties of conventional and additive manufactured Inconel 718 (IN718) after solution and aging (SA) heat treatment were measured at room temperature, 350 °C, and 650 °C. Nanoindentation technique was used to obtain material properties including hardness, reduced modulus, creep rate, creep stress exponent, and thermal activation volume. The indentation size effect (ISE) was analyzed at each temperature. The reduced modulus was measured to decrease by 26% for the conventional samples and by 22% for AM samples as temperature increases from room temperature to 650 °C. The nanoindentation hardness decreases by 19% for the conventional samples and 16% for the AM samples. During the creep tests at 650 °C, the creep stress exponent was found in the range of 8–18, indicating that the deformation at the examined nano/micro scale is controlled by the dislocation climb mechanism.

Survival Survey of Lactobacillus acidophilus In Additional Probiotic Bread

Bread is a popular food in the world because of its variety and convenience. Currently, studies on the adding probiotics to bread are limited due to the adverse effects of processing, such as baking temperature, aerobic environment to the probiotic bacteria. The objective of this study was to produce probiotic cream bread, in which Lactobacillus acidophilus was microencapsulated with Alginate 2% (A); Alginate 2% + maltodextrin 1% (AM); Alginate 2% + xanthan gum 0.1% (AX); and Alginate 2% + maltodextrin 1% + xanthan gum 0.1% (AMX). Microcapsules were added to the kernel, conducting encapsulation yield investigations, survival in baking, preservation of bread, and in simulated gastric fluid and simulated intestinal fluid conditions after 8 days of storage. The results showed that the addition of xanthan gum enhanced the encapsulation yield, it reached 92.9% and 92.37% in AMX and AX samples, respectively. The viability of L. acidophilus during baking was decreased by 3.64 and 3.75 Log (CFU/bread) in AMX and AM samples, compared to A and AX which were decreased by 4.75 and 4.44 Log (CFU/ bread). In SGF (Simulated Gastric Fluid) and SIF (Simulated Intestinal Fluid) conditions, the AMX microcapsules provide the best probiotic protection among the four tested carriers. The combination of xanthan gum and maltodextrin in alginate matrix, eventually leading to having dual efficiency: First, xanthan gum would act as buffers that reduce acid activity; Second, maltodextrin acting as a protective agent of L. acidophilus against high temperature as well as potential prebiotic that improve the viability of probiotic.

Microbial loads on selected fresh blueberry packing lines

Foodborne outbreaks have been linked to the consumption of blueberries contaminated with pathogenic bacteria. The microbial quality of blueberries could be influenced by the conditions of hygiene prevailing during post harvest handling. This study evaluated the hygienic conditions of 6 selected fresh blueberry packing lines. Five of the packing lines were sampled twice and the remaining one was sampled once during the summer of 2015 and the summer of 2017. A delimited area (100 cm2) on each of the ten selected sites of the packing lines was swabbed with sterile sponges before the packing started (AM samples), during lunchtime break (NOON samples), and at the end of a packing day (PM samples). The sponges were thoroughly rinsed with Dey-Engley neutralization broth which was subsequently sampled for total aerobes, yeasts and molds, total coliforms, fecal coliforms, and enterococci. Results showed that sample site and sampling time had a significant influence (P ≤ 0.05) on total aerobic, yeast and mold, and total coliform counts. The PM samples had significantly higher (P ≤ 0.05) total aerobic and yeast and mold counts than the NOON samples which had significantly higher (P ≤ 0.05) counts than the AM samples. Fourty-six out of the 310 (14.8%) collected samples tested positive for enterococci while 27 (8.7%) samples tested positive for fecal coliforms. Berry lugs, rubber belts on color sorters, and premature berry disposing areas had significantly higher (P ≤ 0.05) microbial counts than the other sites. The study suggests that some sites along fresh blueberry packing lines could become contaminated by microorganisms during packing. Whether these contaminated sites will become a food safety concern depends on the incidence of pathogen presence in the microbial community and efficacy of routine sanitizing treatments.

Surface contamination in the operating room: use of adenosine triphosphate monitoring.

We prospectively investigated contamination of high-contact surfaces in the operating room (OR) using adenosine triphosphate (ATP) monitoring. We tested whether contamination would increase from morning (AM) to afternoon (PM), despite cleaning between cases. Second, we compared the degree of OR contamination to non-OR control sites. ORs with high case volumes were selected for the study. Ten sites in each OR were swabbed using the AccuPoint® HC ATP Sanitation Monitoring device, which provided a numerical measure of contamination (relative light units, RLUs). According to the manufacturer, surfaces are considered clean at ≤ 400 RLUs. AM measurements were taken before the start of surgical cases and PM measurements were taken after cases were completed. Eighty morning and 70 afternoon samples were obtained from 8 ORs. Apart from the OR floor, laryngoscope handles had the highest level of morning contamination (1204 RLUs, interquartile range 345, 2603), with 75% of AM samples and 100% of PM samples exceeding 400 RLUs. This contamination was comparable to hospital toilet seats (87% of samples exceeding 400 RLUs). No sites showed statistically significant increases in contamination from AM to PM. Apart from the OR floors, laryngoscope handles emerged as a key OR site where improved cleaning practices may reduce cross-contamination risk. While some sites showed increased contamination over the course of the day, none of these met statistical significance thereby offering tentative evidence that current cleaning practices during case turnover are effective for most sites.

Recent developments for AMS at the Munich tandem accelerator

The AMS setup at the Maier-Leibnitz-Laboratory (MLL) in Garching features a 14 MV tandem accelerator and two dedicated beam lines for high-sensitivity measurements of isotopes in all mass ranges. Especially in the medium mass range (70 < A < 120), AMS sensitivity is often limited by isobaric and isotopic background with only small relative difference in Z and/or A. Here, we present recent developments and upgrades at the MLL with special focus on improved sensitivity and new techniques for challenging AMS isotopes such as 93Zr and 99Tc. Upgrades of the measurement setup as well as radiopurity studies for AMS samples, which could be altered by atmospheric neutrons during transportation by aircraft, are discussed.

Effects of thickness and orientation on the small scale fracture behaviour of additively manufactured Ti-6Al-4V

The effects of sample location, orientation, and thickness on the microstructure and resulting tensile properties of miniature SLM and SEBM AM samples of Ti-6Al-4V has been determined. Microstructure and mechanical property variations in the miniature samples are shown to be related to build orientation and also partly to specimen thickness and position within the build chamber. The present work is our initial attempt to develop a systematic approach for characterization of the microstructure (including defects via tomography) and mechanical properties on miniature AM test specimens that can also be used to reveal issues related to process stability (e.g. fluctuations in build conditions). The discussion is also included regarding their relevance to miniature samples that can be manufactured along with parts, excised from larger samples, and/or excised from actual manufactured components.

English

Urinary sodium excretion is used as an assessment tool for salt intake and salt handling. Even though cumbersome, the most reliable and readily used method in clinical and epidemiological studies is the 24-hour urine collection. This study investigates other appropriate means ofpredicting 24-hour urinary sodium excretion in a sample of Afro-Caribbeans in Barbados by assessing the correlation of actual and estimated urinary sodium excretion between a 24-hour urine collection sample, 12-hour (AM and PM), and spot (AM and PM) urine collections. A convenient sample of 30 healthy participants of Afro-Caribbean origin between the ages of 21 and 55 years was recruited for the study. The 24-hour urine samples and anthropometric data were collected as documented in the study's standard clinical procedure. A 24-hour urine sample was collected as two separate 12-hour AM and PM samples. In addition, two spot samples (AM and PM) were taken during each 12-hour sample collection period. Analysis of the urinary sodium and creatinine was done with a Roche/Hitachi Modular System (Roche Diagnostics, IN, USA). SPSS version 19 was used to analyse the data to make inferences. Thirty Afro-Caribbean subjects participated in this study: 16 females and 14 males. The average age and body mass index (BMI) were 38 +/- 17 years and 25.32 +/- 5.98 kg/m2, respectively. The greatest correlation of the estimated 24-hour sodium excretion to the measured 24-hour sodium excretion was observed in the 12-hour PM sample (Pearson's correlation, r = 0.786, p < 0.001) followed by the 12-hour AM sample (Pearson's correlation, r = 0.774, p < 0.001). The PM spot sample showed a weaker, but still statistically significant correlation to the 24-hour timed sample (Pearson 's correlation, r = 0.404, p < 0.045). The AM spot sample showed a very weak and insignificant correlation (Pearson 's correlation, r = 0.05, p = 0.807) to the 24-hour timed sample. Similarly to the whole sample, the gender analysis demonstrated that estimated 24-hour sodium excretion in the female's 12-hour PM sample had the greatest correlation (r = 0.819, p < 0.001) to the measured 24-hour sodium excretion, followed by the 12-hour AM (r = 0.793, p = 0.001) and the PM spot samples (r = 0.741, p = 0.02). The correlation between variables is weaker in males compared to the females. Overall, this study shows a clear correlation between the estimated 24-hour sodium excretion from the 12-hour timed PM sample and the measured 24-hour sodium excretion. Such findings support the thought of using other alternatives to determine sodium excretion, in view of replacing the cumbersome 24-hour urinary collection with a smaller timed sample. Nonetheless, a more robust and randomized population sample as well as a method to correct for high creatinine variability is required to further enhance the significance of the obtained results.

Holocene evolution and geochronology of a semiarid fluvial system in the western slope of the Central Andes: AMS 14C data in El Tránsito River Valley, Northern Chile

Abstract In this paper, we discriminate the contribution of the different sediment sources into a river situated in the semiarid region of northern Chile, differentiating the ones driven by the paraglacial response from the ones yielded to the tributary-junction alluvial fans or the ones coming from the hillslopes. The sedimentary infilling is accurately described in the main landforms such as alluvial fans, alluvial terraces and landslides in the current valley floor where twenty-six 14C AMS samples were picked up. The 14C age data indicate that the aggradation in the uppermost part of the valley immediately postdates the glacial retreat at ∼15,000 14C years cal. B.P. and spans the whole Holocene starting at 11 ka. B.P. and finishing about 2 ka B.P. The main sources for lateral inputs are debris flows from tributary catchments in the portion where the river is embedded in between 1000 and 2000 m a.s.l as well as catastrophic landslides. Additionally, an extensive detailed geomorphological mapping is provided to discuss the meaning of the ages together with an assessment of where the samples came from. Finally, the dataset and field criteria provided in this work contribute to better perform paleoclimatological interpretations for the semiarid fluvial systems of northern Chile. These interpretations usually consider the increased influence of the westerlies during the Holocene and the span of time that the paraglacial response delivers glacigenic sediments into the system.

Flood frequency analysis for a braided river catchment in New Zealand: Comparing annual maximum and partial duration series with varying record lengths

This study addresses technical questions concerning the use of the partial duration series (PDS) within the domain of flood frequency analysis. The recurring questions which often prevent the standardised use of the PDS are peak independence and threshold selection. This paper explores standardised approaches to peak and threshold selection to produce PDS samples with differing average annual exceedances, using six theoretical probability distributions. The availability of historical annual maximum (AMS) data (1930–1966) in addition to systemic AMS data (1967–2015) enables a unique comparison between the performance of the PDS sample and the systemic AMS sample. A recently derived formula for the translation of the PDS into the annual domain, simplifying the use of the PDS, is utilised in an applied case study for the first time. Overall, the study shows that PDS sampling returns flood magnitudes similar to those produced by AMS series utilising historical data and thus the use of the PDS should be preferred in cases where historical flood data is unavailable.