Preservation and Distributions of Covalently Bound Polyaromatic Hydrocarbons in Ancient Biogenic Kerogens and Insoluble Organic Macromolecules

The likelihood of finding pristine molecular biosignatures preserved in Earth's oldest rocks or on other planetary bodies is low, and new approaches are needed to assess the origins of highly altered and recalcitrant organic matter. In this study, we aim to understand the distributions and systematics of preservation of ancient polycyclic aromatic hydrocarbons (PAHs), as both free hydrocarbons and bound within insoluble macromolecules. We report the distributions of bound PAHs generated by catalytic hydropyrolysis from ancient biogenic kerogens and from insoluble organic matter (IOM) in high-temperature carbonaceous residues from pyrobitumens and synthetic coke. For biogenic kerogens, the degree of thermal maturity exerts the primary control on the preservation and distributions of the major five-ring and six-ring PAH compounds. This holds for both Precambrian and Phanerozoic rocks, thus source variation in primary biogenic organic matter inputs does not exert the major control on bound PAH. The IOM samples, predominantly residues from hydrocarbon cracking at high temperatures, preserve a bound PAH profile significantly distinct from ancient biogenic kerogens and characterized by an absence of perylene and higher abundance of large-ring condensed PAHs. Covalently bound PAH profiles offer promise as "last resort" molecular biosignatures for aiding the astrobiological search for ancient life.

A late Paleoproterozoic (1.74 Ga) deep-sea, low-temperature, iron-oxidizing microbial hydrothermal vent community from Arizona, USA

Modern marine hydrothermal vents occur in a wide variety of tectonic settings and are characterized by seafloor emission of fluids rich in dissolved chemicals and rapid mineral precipitation. Some hydrothermal systems vent only low-temperature Fe-rich fluids, which precipitate deposits dominated by iron oxyhydroxides, in places together with Mn-oxyhydroxides and amorphous silica. While a proportion of this mineralization is abiogenic, most is the result of the metabolic activities of benthic, Fe-oxidizing bacteria (FeOB), principally belonging to the Zetaproteobacteria. These micro-organisms secrete micrometer-scale stalks, sheaths, and tubes with a variety of morphologies, composed largely of ferrihydrite that act as sacrificial structures, preventing encrustation of the cells that produce them. Cultivated marine FeOB generally require neutral pH and microaerobic conditions to grow. Here, we describe the morphology and mineralogy of filamentous microstructures from a late Paleoproterozoic (1.74 Ga) jasper (Fe-oxide-silica) deposit from the Jerome area of the Verde mining district in central Arizona, USA, that resemble the branching tubes formed by some modern marine FeOB. On the basis of this comparison, we interpret the Jerome area filaments as having formed by FeOB on the deep seafloor, at the interface of weakly oxygenated seawater and low-temperature Fe-rich hydrothermal fluids. We compare the Jerome area filaments with other purported examples of Precambrian FeOB and discuss the implications of their presence for existing redox models of Paleoproterozoic oceans during the "Boring Billion."

Triple iron isotope constraints on the role of ocean iron sinks in early atmospheric oxygenation

The role that iron played in the oxygenation of Earth's surface is equivocal. Iron could have consumed molecular oxygen when Fe³⁺-oxyhydroxides formed in the oceans, or it could have promoted atmospheric oxidation by means of pyrite burial. Through high-precision iron isotopic measurements of Archean-Paleoproterozoic sediments and laboratory grown pyrites, we show that the triple iron isotopic composition of Neoarchean-Paleoproterozoic pyrites requires both extensive marine iron oxidation and sulfide-limited pyritization. Using an isotopic fractionation model informed by these data, we constrain the relative sizes of sedimentary Fe³⁺-oxyhydroxide and pyrite sinks for Neoarchean marine iron. We show that pyrite burial could have resulted in molecular oxygen export exceeding local Fe²⁺ oxidation sinks, thereby contributing to early episodes of transient oxygenation of Archean surface environments.

The geologic history of seawater oxygen isotopes from marine iron oxides

The oxygen isotope composition (δ¹⁸O) of marine sedimentary rocks has increased by 10 to 15 per mil since Archean time. Interpretation of this trend is hindered by the dual control of temperature and fluid δ¹⁸O on the rocks' isotopic composition. A new δ¹⁸O record in marine iron oxides covering the past ~2000 million years shows a similar secular rise. Iron oxide precipitation experiments reveal a weakly temperature-dependent iron oxide-water oxygen isotope fractionation, suggesting that increasing seawater δ¹⁸O over time was the primary cause of the long-term rise in δ¹⁸O values of marine precipitates. The ¹⁸O enrichment may have been driven by an increase in terrestrial sediment cover, a change in the proportion of high- and low-temperature crustal alteration, or a combination of these and other factors.

Microbially induced potassium enrichment in Paleoproterozoic shales and implications for reverse weathering on early Earth

Illitisation requires potassium incorporation into a smectite precursor, a process akin to reverse weathering. However, it remains unclear whether microbes facilitate K+ uptake to the sediments and whether illitisation was important in the geological past. The 2.1 billion-year-old Francevillian Series of Gabon has been shown to host mat-related structures (MRS) and, in this regard, these rocks offer a unique opportunity to test whether ancient microbes induced illitisation. Here, we show high K content confined to illite particles that are abundant in the facies bearing MRS, but not in the host sandstone and black shale. This observation suggests that microbial biofilms trapped K+ from the seawater and released it into the pore-waters during respiration, resulting in illitisation. The K-rich illite developed exclusively in the fossilized MRS thus provides a new biosignature for metasediments derived from K-feldspar-depleted rocks that were abundant crustal components on ancient Earth.

Electric vehicle sound stimuli data and enhancements

Data for six electric vehicle WOT interior sound measurements and eight enhanced sound signatures are presented. The measurement of electric vehicle interior sound signature data and the enhancement of these stimuli are documented in this data article. The procedures and equipment that were used to record the data, as well as the transposition, harmony and order addition, frequency filtering and modulation enhancement techniques that were applied to these stimuli are explained in detail. The transient frequency content of the 12 sound stimuli is presented in acoustic spectrograms along with the audio files in.mp3 format.

Data for indirect load case estimation of ice-induced moments from shaft line torque measurements

During ice navigation, blade measurements of ice-induced moments on ship propellers, are challenged by the harsh operating environment. To overcome this problem, shaft line measurements are performed inboard, and the required propeller loads are subsequently estimated using a dynamic model and the solution of an inverse problem. The inverse problem is mathematically ill-posed and requires the determination of the ice-induced moment on the propeller blades from shaft line measurements. Full-scale torsional response data is presented as calculated from indirect strain measurements on the shaft line of a polar supply and research vessel. The vessel operated on a 68-day voyage between Cape Town and Antarctica and spent almost 11 days in sea ice with observed concentrations above 90% and a maximum thickness of 3 m. Data for five ice-induced load cases are presented, including the shaft torque from indirect measurements and the estimated ice-induced moment, which is obtained by solving an ill-posed inverse problem. The ice-induced moments on the propeller are obtained by approximating the drive-train as a viscously damped, elastic lumped mass model. The ice-induced moment is then determined through existing approaches to solving the ill-conditioned inverse problem. The lumped mass model is presented along with algorithms to solve the inverse problem, including truncated singular value decomposition, truncated generalized singular value decomposition and Tikhonov׳s method. The resulting time series data for the inversely calculated ice-induced moments is published to provide industry with load cases for ice-going propulsion design.

Ediacara biota flourished in oligotrophic and bacterially dominated marine environments across Baltica

Middle-to-late Ediacaran (575–541 Ma) marine sedimentary rocks record the first appearance of macroscopic, multicellular body fossils, yet little is known about the environments and food sources that sustained this enigmatic fauna. Here, we perform a lipid biomarker and stable isotope (δ¹⁵N_total and δ¹³C_TOC) investigation of exceptionally immature late Ediacaran strata (<560 Ma) from multiple locations across Baltica. Our results show that the biomarker assemblages encompass an exceptionally wide range of hopane/sterane ratios (1.6–119), which is a broad measure of bacterial/eukaryotic source organism inputs. These include some unusually high hopane/sterane ratios (22–119), particularly during the peak in diversity and abundance of the Ediacara biota. A high contribution of bacteria to the overall low productivity may have bolstered a microbial loop, locally sustaining dissolved organic matter as an important organic nutrient. These oligotrophic, shallow-marine conditions extended over hundreds of kilometers across Baltica and persisted for more than 10 million years.

The environments and food sources that sustained Ediacara biota 575-541 million years ago remain unclear. Here, the authors perform lipid biomarker and isotopic analyses on biota fossil-containing Ediacaran strata from Baltica and propose the presence of a microbial loop bolstered by bacteria.

Human responses to wave slamming vibration on a polar supply and research vessel

A polar supply and research vessel is pre-disposed to wave slamming which has caused complaints among crew and researchers regarding interference with sleep, equipment use and research activities. The present work undertook to survey passenger claims of sleep interference, disturbed motor tasks and equipment damage as a result of wave slamming during normal operations of this vessel. The hypothesis was investigated that whole-body vibration metrics from ISO 2631-1 are potentially suitable for the prediction of human slamming complaints. Full-scale acceleration measurements were performed and wave slamming events were subsequently identified from the human weighted acceleration time histories. A daily diary survey was also conducted to gather the human response. The vibration caused by wave slamming was found to be strongly correlated with sleep disturbances and activity interference. Sleep and equipment use were found to be the most affected parameters by slamming. Daily vibration dose values were determined by accumulating the vibration as a result of slamming over 24 h periods. This metric accounted for increased magnitudes and frequency of slamming incidents and proved to be the best metric to represent human responses to slamming vibration. The greatest percentage of activities affected by slamming related to sleep regardless of daily cumulative VDV magnitude. More than 50% of the recorded responses related to sleep when the daily cumulative VDV ranged between 8.0 m/s^1.75-10.0 m/s^1.75. The peak vertical vibration levels recorded on the vessel reach magnitudes which are associated with sleep disturbance in environments where acoustic noise is present.

Bioavailability of two licensed paediatric rifampicin suspensions: implications for quality control programmes

SETTING

To assess the revised World Health Organization-recommended dose of 10-20 mg/kg rifampicin (RMP), we studied the steady state pharmacokinetics of RMP in South African children who received standard treatment for drug-susceptible tuberculosis (TB).

OBJECTIVE

To determine the formulation effect on the pharmacokinetics of RMP.

DESIGN

RMP plasma concentrations were characterised in 146 children (median age 1.4 years, range 0.2-10.2). The morning dose on the day of the pharmacokinetic evaluation was administered as one of two RMP single-drug oral suspensions.

RESULTS

While one formulation achieved 2 h concentrations in the range of those observed in adults (median 6.54 mg/l, interquartile range [IQR] 4.47-8.84), the other attained a median bioavailability of only 25% of this, with a median 2 h concentration of 1.59 mg/l (IQR 0.89-2.38).

CONCLUSION

RMP is a key drug for the treatment of TB. It is critical that the quality of RMP suspensions used to treat childhood TB is ensured.

Infectious disease exposures and outbreaks at a South African neonatal unit with review of neonatal outbreak epidemiology in Africa

BACKGROUND

Hospitalized neonates are vulnerable to infection, with pathogen exposures occurring in utero, intrapartum, and postnatally. African neonatal units are at high risk of outbreaks owing to overcrowding, understaffing, and shared equipment.

METHODS

Neonatal outbreaks attended by the paediatric infectious diseases and infection prevention (IP) teams at Tygerberg Children's Hospital, Cape Town (May 1, 2008 to April 30, 2016) are described, pathogens, outbreak size, mortality, source, and outbreak control measures. Neonatal outbreaks reported from Africa (January 1, 1996 to January 1, 2016) were reviewed to contextualize the authors' experience within the published literature from the region.

RESULTS

Thirteen outbreaks affecting 148 babies (11 deaths; 7% mortality) over an 8-year period were documented, with pathogens including rotavirus, influenza virus, measles virus, and multidrug-resistant bacteria (Serratia marcescens, Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus, and vancomycin-resistant enterococci). Although the infection source was seldom identified, most outbreaks were associated with breaches in IP practices. Stringent transmission-based precautions, staff/parent education, and changes to clinical practices contained the outbreaks. From the African neonatal literature, 20 outbreaks affecting 524 babies (177 deaths; 34% mortality) were identified; 50% of outbreaks were caused by extended-spectrum β-lactamase-producing Klebsiella pneumoniae.

CONCLUSIONS

Outbreaks in hospitalized African neonates are frequent but under-reported, with high mortality and a predominance of Gram-negative bacteria. Breaches in IP practice are commonly implicated, with the outbreak source confirmed in less than 50% of cases. Programmes to improve IP practice and address antimicrobial resistance in African neonatal units are urgently required.

A Bayesian analysis for censored Rayleigh model using a generalised hypergeometric prior

Based on a type II censored sample, Bayesian estimation for the scale parameter of the Rayleigh model is carried out under the assumption of the squared error loss function. A generalised hypergeometric distribution with its versatile shape of tails is introduced as a prior, and beta special cases are examined. A simulation study is carried out to investigate the sensitivity of four special cases of this beta prior family in terms of bias, frequentist coverage and mean square error and to determine their effect on robustness. Prediction bounds are derived for the lifetime of unused components using this beta prior family. A data set is used to illustrate and support some of the findings.

Peri-Operative Inflammatory Cytokines in Plasma of the Elderly Correlate in Prospective Study with Postoperative Changes in Cognitive Test Scores

Increasingly, postoperative cognitive dysfunction (POCD) is recognized as a complication after surgery in the elderly; but it's etiology remains unclear. Here we examine changes in cytokine levels during both the pre-operative and postoperative period, comparing them with long term variation in cognitive test scores. Forty-one patients aged 65 and older undergoing major surgery with general anesthesia were recruited after written consent in this IRB approved study. Thirty went on to complete this prospective, non-interven-tional and non-randomized study. Plasma levels of cytokines Il-6, Il-8, Il-10, and TNF were determined using ELISA with MILLIPLEX Multi-Analyte Profiling (Billerica, MA). All subjects had neurocognitive tests pre-operatively and 6 months post-surgery, including Paragraph Recall Immediate and Delayed, Digit Span Forward (DSF) and Backward (DSB), and Trail Making A and B. Spearman's Rho and repeated measure rank analysis were used to examine the dependence of z score changes in cognitive tests (baseline versus 6 months) as a function of 3 cytokine time points (presurgical, post anesthesia care unit (PACU), and post-operative day one (POD1)). A greater increase in PACU inflammatory burden correlated with a greater decline in performance on the DSB (IL6, IL8; r>-0.560; p<= 0.008). DSF changes correlated slightly better with pre-surgical cytokines, declining more with higher cytokines (IL6, r= -0.551, p=0.002; IL8, -0.468, 0.009). TNF, examining all 3 values, changed only slightly postoperatively, but still correlated with a decline in DSB (p=0.014). Thus, cognitive performance, over 6 months post surgery, declines with elevated perioperative inflammation. Specific cytokines at specific perioperative times may impact specific cognitive functions, serving as diagnostics as well as contributing causation.

Pharmacokinetics of Rifampin, Isoniazid, Pyrazinamide, and Ethambutol in Infants Dosed According to Revised WHO-Recommended Treatment Guidelines

There are limited pharmacokinetic data for use of the first-line antituberculosis drugs during infancy (<12 months of age), when drug disposition may differ. Intensive pharmacokinetic sampling was performed in infants routinely receiving antituberculosis treatment, including rifampin, isoniazid, pyrazinamide, and ethambutol, using World Health Organization-recommended doses. Regulatory-approved single-drug formulations, including two rifampin suspensions, were used on the sampling day. Assays were conducted using liquid chromatography-mass spectrometry; pharmacokinetic parameters were generated using noncompartmental analysis. Thirty-nine infants were studied; 14 (36%) had culture-confirmed tuberculosis. Fifteen (38%) were premature (<37 weeks gestation); 5 (13%) were HIV infected. The mean corrected age and weight were 6.6 months and 6.45 kg, respectively. The mean maximum plasma concentrations (Cmax) for rifampin, isoniazid, pyrazinamide, and ethambutol were 2.9, 7.9, 41.9, and 1.3 μg/ml, respectively (current recommended adult target concentrations: 8 to 24, 3 to 6, 20 to 50, and 2 to 6 μg/ml, respectively), and the mean areas under the concentration-time curves from 0 to 8 h (AUC0-8) were 12.1, 24.7, 239.4, and 5.1 μg · h/ml, respectively. After adjusting for age and weight, rifampin exposures for the two formulations used differed inCmax(geometric mean ratio [GMR],2.55; 95% confidence interval [CI], 1.47 to 4.41;P= 0.001) and AUC0-8(GMR, 2.52; 95% CI, 1.34 to 4.73;P= 0.005). HIV status was associated with lower pyrazinamideCmax(GMR, 0.85; 95% CI, 0.75 to 0.96;P= 0.013) and AUC0-8(GMR, 0.79; 95% CI, 0.69 to 0.90;P< 0.001) values. No other important differences were observed due to age, weight, prematurity, ethnicity, or gender. In summary, isoniazid and pyrazinamide concentrations in infants compared well with proposed adult target concentrations; ethambutol concentrations were lower but similar to previously reported pediatric studies. The low rifampin exposures require further investigation. (This study has been registered at ClinicalTrials.gov under registration no. NCT01637558.).

Comparison of the growth kinetics and proteolytic activities of Chryseobacterium species and Pseudomonas fluorescens

The effect of temperature on the growth kinetics and proteolytic activity of Chryseobacterium joostei and Chryseobacterium bovis was determined during this study. The results were compared with the activities of Pseudomonas fluorescens, which is regarded to be a major food spoilage psychrotolerant microorganism. For the growth studies, cultures were incubated in nutrient broth in a temperature gradient incubator (from 9 to 50 °C) and separately at 4 °C, and the optical density was measured at different time intervals. Growth temperature profiles for each organism were constructed. For determination of proteolytic activity, the cultures were incubated in fat-free ultra-high temperature processed milk in the temperature gradient incubator for 72 h (temperature range as above). Cell-free extracts were used to determine the proteolytic activity using the azocasein method. Results of the growth studies showed that C. joostei had the ability to grow over a wider temperature range than C. bovis and P. fluorescens without being affected by changes in the temperature. For the proteolytic activity, C. joostei had significantly (p < 0.001) higher activity per milligram of protein at 15.5 °C, followed by C. bovis and P. fluorescens. The results showed that C. joostei potentially has an even greater spoilage capacity in milk on the basis of growth rate and proteolytic activity than did P. fluorescens.

Bloodstream infections and antimicrobial resistance patterns in a South African neonatal intensive care unit

BACKGROUND

Bloodstream infections remain a leading cause of morbidity and mortality in neonatal intensive care units (NICU) worldwide. Commonly isolated NICU pathogens are increasingly resistant to standard antimicrobial treatment regimes.

OBJECTIVES

The primary aim of this study was to determine the burden of bloodstream infections (BSI) in an NICU in a low-to-middle-income country and to describe the spectrum of pathogens isolated together with their drug susceptibility patterns.

METHODS

This retrospective, descriptive study included NICU patients admitted to the Tygerberg Children's Hospital, Cape Town, between 1 January and 31 December 2008. All blood culture samples submitted to the reference laboratory were extracted and clinical data on patients were obtained by hospital record review.

RESULTS

There were 78 culture-confirmed episodes of BSI in 54/503 (11%) patients admitted; median gestational age was 31 weeks (IQR 29-37) and birth weight 1370 g (IQR 1040-2320). Common isolates included coagulase-negative Staphylococcus (22/78, 28%), Klebsiella spp. (17/78, 22%), Acinetobacter spp. (14/78, 18%), Candida spp. (9/78, 11·5%) and methicillin-resistant Staphylococcus aureus (5/78, 6%). There was a predominance of gram-negative organisms (38/78, 48·7%). All Staphylococcus aureus isolates were methicillin-resistant and 59% of Klebsiella pneumoniae isolates were extended spectrum β-lactamase (ESBL) producers. Acinetobacter baumanii isolates showed low susceptibility to the aminoglycosides, carbapenems and cephalosporins. Of 54 infants admitted to the NICU with BSI, 25 (46%) died; 9/25 deaths (36%) were attributable solely to infection.

CONCLUSION

Compared with overall mortality in the NICU, that attributable solely or partly to BSI was high. Many bacterial BSI isolates were resistant to current empiric antibiotic regimens. Regular microbiological and clinical surveillance of BSI in NICUs is required to inform appropriate antibiotic protocols and monitor the impact of infection prevention strategies.

A Randomized, Double Blind Study to Evaluate the Efficacy of Palonosetron with Dexamethasone Versus Palonosetron Alone for Prevention of Post-Operative Nausea and Vomiting in Subjects Undergoing Bariatric Surgeries with High Emetogenic Risk

Introduction:

Postoperative (PONV) and postdischarge (PDNV) nausea and vomiting are common (60-70%) after bariatric surgery. Palonosetron (Pal), a novel 5-HT3 antagonist, is an effective antiemetic with a prolonged duration of action in the setting of PDNV. We hypothesized that combination therapy with Palonosetron (Pal) and dexamethasone (Dex) would improve treatment in comparison to Palonosetron alone in patients at high risk for PONV.

Methods:

In this study, patients undergoing bariatric laparoscopic surgery under general anesthesia, a subgroup of a larger Phase IV clinical trial of patients who had laparoscopic surgery, were randomized to 8 mg Dex + 0.075mg Pal or saline + 0.075mg Pal. Data was collected postoperatively at 2, 6, 24 and 72 hrs. A Functional Living Index-Emesis (QOL-FLIE) test was administered at 96 hrs.

Results:

We enrolled 76 ASA 1-2 patients with at least 3 PONV risk factors. Both randomization groups had a low incidence of vomiting in the PACU (Pal, 0.0%; Pal + Dex, 5.4%) as well as at 72 hours (0.0% both groups). Complete response (no vomiting, no rescue medication) was not different between treatment groups at any time intervals. Cumulative success rates over the entire 72 hrs were 60.4% (Pal alone) vs. 60.0% (Pal + Dex). Nausea scores (4 point ordinal scale) were not different between groups for any time intervals. Cumulative success scores for nausea (score = “none”; 0-72 hrs) were 41.9% for the Pal group, and 55.2% for the Pal+ Dex group. The Pal + Dex group showed a trend toward greater satisfaction on the QOL-FLIE scores with the greatest differences in the “nausea domain”.

Discussion:

The combination therapy (Pal + Dex) did not significantly reduce the incidence of PONV or PDNV when compared with Pal alone although a trend was observed indicating the possible increased efficacy of multi-drug therapy. There was no change in comparative efficacy over 72 hrs, possibly due to the low incidence of PDNV in both groups.

Sulfur record of rising and falling marine oxygen and sulfate levels during the Lomagundi event

Carbonates from approximately 2.3-2.1 billion years ago show markedly positive δ(13)C values commonly reaching and sometimes exceeding +10‰. Traditional interpretation of these positive δ(13)C values favors greatly enhanced organic carbon burial on a global scale, although other researchers have invoked widespread methanogenesis within the sediments. To resolve between these competing models and, more generally, among the mechanisms behind Earth's most dramatic carbon isotope event, we obtained coupled stable isotope data for carbonate carbon and carbonate-associated sulfate (CAS). CAS from the Lomagundi interval shows a narrow range of δ(34)S values and concentrations much like those of Phanerozoic and modern marine carbonate rocks. The δ(34)S values are a close match to those of coeval sulfate evaporites and likely reflect seawater composition. These observations are inconsistent with the idea of diagenetic carbonate formation in the methanic zone. Toward the end of the carbon isotope excursion there is an increase in the δ(34)S values of CAS. We propose that these trends in C and S isotope values track the isotopic evolution of seawater sulfate and reflect an increase in pyrite burial and a crash in the marine sulfate reservoir during ocean deoxygenation in the waning stages of the positive carbon isotope excursion.

High tuberculosis exposure among neonates in a high tuberculosis and human immunodeficiency virus burden setting

BACKGROUND

Maternal and neonatal tuberculosis (TB) are under-recognised, particularly in settings with a high burden of human immunodeficiency virus (HIV) infection.

DESIGN AND SETTING

Retrospective audit of neonates routinely screened for TB in a South African hospital during 2009. Surveillance sources reviewed included routine clinical, laboratory and pharmacy records.

RESULTS

Among 70 neonates (60% HIV-exposed) screened for TB, the median gestational age was 35.5 weeks (IQR 33-38), and the median birth weight was 2000 g (IQR 1530-2484). The neonates were grouped according to a history of documented TB exposure: maternal TB in 41/70 (59%), suspected maternal TB in 9/70 (13%), other documented household TB exposure in 5/70 (7%), and no known TB exposure 15/70 (21%). Of the 50 neonates exposed to confirmed or suspected maternal TB, 36 (72%) were initiated on TB chemoprophylaxis, 5 (10%) received TB treatment and 9 (18%) received no intervention. Eight (8/50, 16%) were diagnosed with TB, all of whom were born to mothers with suspected or proven TB.

CONCLUSIONS

Maternal TB, primarily among HIV-infected women, was the main indication for TB screening of neonates. Routine TB screening of pregnant women and TB care in mothers and infants should be improved in settings with a high burden of TB and HIV.

Deposition of 1.88-billion-year-old iron formations as a consequence of rapid crustal growth

Iron formations are chemical sedimentary rocks comprising layers of iron-rich and silica-rich minerals whose deposition requires anoxic and iron-rich (ferruginous) sea water. Their demise after the rise in atmospheric oxygen by 2.32 billion years (Gyr) ago has been attributed to the removal of dissolved iron through progressive oxidation or sulphidation of the deep ocean. Therefore, a sudden return of voluminous iron formations nearly 500 million years later poses an apparent conundrum. Most late Palaeoproterozoic iron formations are about 1.88 Gyr old and occur in the Superior region of North America. Major iron formations are also preserved in Australia, but these were apparently deposited after the transition to a sulphidic ocean at 1.84 Gyr ago that should have terminated iron formation deposition, implying that they reflect local marine conditions. Here we date zircons in tuff layers to show that iron formations in the Frere Formation of Western Australia are about 1.88 Gyr old, indicating that the deposition of iron formations from two disparate cratons was coeval and probably reflects global ocean chemistry. The sudden reappearance of major iron formations at 1.88 Gyr ago--contemporaneous with peaks in global mafic-ultramafic magmatism, juvenile continental and oceanic crust formation, mantle depletion and volcanogenic massive sulphide formation--suggests deposition of iron formations as a consequence of major mantle activity and rapid crustal growth. Our findings support the idea that enhanced submarine volcanism and hydrothermal activity linked to a peak in mantle melting released large volumes of ferrous iron and other reductants that overwhelmed the sulphate and oxygen reservoirs of the ocean, decoupling atmospheric and seawater redox states, and causing the return of widespread ferruginous conditions. Iron formations formed on clastic-starved coastal shelves where dissolved iron upwelled and mixed with oxygenated surface water. The disappearance of iron formations after this event may reflect waning mafic-ultramafic magmatism and a diminished flux of hydrothermal iron relative to seawater oxidants.

A case of congenital measles during the 2010 South African epidemic

Congenital measles is a well recognised but uncommon transplacental infection in the post-vaccine era. A 4-day-old infant is described who presented with uncomplicated congenital measles during the 2010 South African measles outbreak. Clinicians working in regions affected by measles outbreaks should be mindful of waning vaccine-induced measles immunity where infections among pregnant women may result in a resurgence of congenital measles.

Geological constraints on the origin of oxygenic photosynthesis

This article examines the geological evidence for the rise of atmospheric oxygen and the origin of oxygenic photosynthesis. The evidence for the rise of atmospheric oxygen places a minimum time constraint before which oxygenic photosynthesis must have developed, and was subsequently established as the primary control on the atmospheric oxygen level. The geological evidence places the global rise of atmospheric oxygen, termed the Great Oxidation Event (GOE), between ~2.45 and ~2.32 Ga, and it is captured within the Duitschland Formation, which shows a transition from mass-independent to mass-dependent sulfur isotope fractionation. The rise of atmospheric oxygen during this interval is closely associated with a number of environmental changes, such as glaciations and intense continental weathering, and led to dramatic changes in the oxidation state of the ocean and the seawater inventory of transition elements. There are other features of the geologic record predating the GOE by as much as 200-300 million years, perhaps extending as far back as the Mesoarchean-Neoarchean boundary at 2.8 Ga, that suggest the presence of low level, transient or local, oxygenation. If verified, these features would not only imply an earlier origin for oxygenic photosynthesis, but also require a mechanism to decouple oxygen production from oxidation of Earth's surface environments. Most hypotheses for the GOE suggest that oxygen production by oxygenic photosynthesis is a precondition for the rise of oxygen, but that a synchronous change in atmospheric oxygen level is not required by the onset of this oxygen source. The potential lag-time in the response of Earth surface environments is related to the way that oxygen sinks, such as reduced Fe and sulfur compounds, respond to oxygen production. Changes in oxygen level imply an imbalance in the sources and sinks for oxygen. Changes in the cycling of oxygen have occurred at various times before and after the GOE, and do not appear to require corresponding changes in the intensity of oxygenic photosynthesis. The available geological constraints for these changes do not, however, disallow a direct role for this metabolism. The geological evidence for early oxygen and hypotheses for the controls on oxygen level are the basis for the interpretation of photosynthetic oxygen production as examined in this review.

Large colonial organisms with coordinated growth in oxygenated environments 2.1 Gyr ago

The evidence for macroscopic life during the Palaeoproterozoic era (2.5-1.6 Gyr ago) is controversial. Except for the nearly 2-Gyr-old coil-shaped fossil Grypania spiralis, which may have been eukaryotic, evidence for morphological and taxonomic biodiversification of macroorganisms only occurs towards the beginning of the Mesoproterozoic era (1.6-1.0 Gyr). Here we report the discovery of centimetre-sized structures from the 2.1-Gyr-old black shales of the Palaeoproterozoic Francevillian B Formation in Gabon, which we interpret as highly organized and spatially discrete populations of colonial organisms. The structures are up to 12 cm in size and have characteristic shapes, with a simple but distinct ground pattern of flexible sheets and, usually, a permeating radial fabric. Geochemical analyses suggest that the sediments were deposited under an oxygenated water column. Carbon and sulphur isotopic data indicate that the structures were distinct biogenic objects, fossilized by pyritization early in the formation of the rock. The growth patterns deduced from the fossil morphologies suggest that the organisms showed cell-to-cell signalling and coordinated responses, as is commonly associated with multicellular organization. The Gabon fossils, occurring after the 2.45-2.32-Gyr increase in atmospheric oxygen concentration, may be seen as ancient representatives of multicellular life, which expanded so rapidly 1.5 Gyr later, in the Cambrian explosion.

Organic-walled microfossils in 3.2-billion-year-old shallow-marine siliciclastic deposits

Although the notion of an early origin and diversification of life on Earth during the Archaean eon has received increasing support in geochemical, sedimentological and palaeontological evidence, ambiguities and controversies persist regarding the biogenicity and syngeneity of the record older than Late Archaean. Non-biological processes are known to produce morphologies similar to some microfossils, and hydrothermal fluids have the potential to produce abiotic organic compounds with depleted carbon isotope values, making it difficult to establish unambiguous traces of life. Here we report the discovery of a population of large (up to about 300 mum in diameter) carbonaceous spheroidal microstructures in Mesoarchaean shales and siltstones of the Moodies Group, South Africa, the Earth's oldest siliciclastic alluvial to tidal-estuarine deposits. These microstructures are interpreted as organic-walled microfossils on the basis of petrographic and geochemical evidence for their endogenicity and syngeneity, their carbonaceous composition, cellular morphology and ultrastructure, occurrence in populations, taphonomic features of soft wall deformation, and the geological context plausible for life, as well as a lack of abiotic explanation falsifying a biological origin. These are the oldest and largest Archaean organic-walled spheroidal microfossils reported so far. Our observations suggest that relatively large microorganisms cohabited with earlier reported benthic microbial mats in the photic zone of marginal marine siliciclastic environments 3.2 billion years ago.

Atmospheric sulfur in Archean komatiite-hosted nickel deposits

Some of Earth's largest iron-nickel (Fe-Ni) sulfide ore deposits formed during the Archean and early Proterozoic. Establishing the origin of the metals and sulfur in these deposits is critical for understanding their genesis. Here, we present multiple sulfur isotope data implying that the sulfur in Archean komatiite-hosted Fe-Ni sulfide deposits was previously processed through the atmosphere and then accumulated on the ocean floor. High-temperature, mantle-derived komatiite magmas were then able to incorporate the sulfur from seafloor hydrothermal sulfide accumulations and sulfidic shales to form Neoarchean komatiite-hosted Fe-Ni sulfide deposits at a time when the oceans were sulfur-poor.

Cryptococcus meningitis and skin lesions in an HIV negative child

Disseminated cryptococcosis is an uncommon occurrence in immunocompetent populations and occurs mainly in immunocompromised patients. The first case of cryptococcus meningitis and skin lesions in a 4-year-old confirmed HIV negative boy who presented with fever, meningism and skin lesions is reported. On examination the child was confused, uncooperative, and had neck stiffness and raised skin lesions. A septic screen, including skin scraping, was performed; the child was treated with penicillin and ceftriaxone for suspected meningococcal meningitis. The cerebrospinal fluid (CSF) had normal protein, glucose and chloride levels; yeasts were observed on Gram stain from the CSF and skin scraping. The India ink stain and Cryptococcus neoformans latex agglutination test on the CSF were both positive. Bacterial culture of the skin biopsy, CSF and blood culture specimens was negative. The child was treated with amphotericin B based on preliminary results, and had a gradual recovery with no neurological sequelae. The child continued oral fluconazole.

Iron isotope constraints on the Archean and Paleoproterozoic ocean redox state

The response of the ocean redox state to the rise of atmospheric oxygen about 2.3 billion years ago (Ga) is a matter of controversy. Here we provide iron isotope evidence that the change in the ocean iron cycle occurred at the same time as the change in the atmospheric redox state. Variable and negative iron isotope values in pyrites older than about 2.3 Ga suggest that an iron-rich global ocean was strongly affected by the deposition of iron oxides. Between 2.3 and 1.8 Ga, positive iron isotope values of pyrite likely reflect an increase in the precipitation of iron sulfides relative to iron oxides in a redox stratified ocean.

Dating the rise of atmospheric oxygen

Several lines of geological and geochemical evidence indicate that the level of atmospheric oxygen was extremely low before 2.45 billion years (Gyr) ago, and that it had reached considerable levels by 2.22 Gyr ago. Here we present evidence that the rise of atmospheric oxygen had occurred by 2.32 Gyr ago. We found that syngenetic pyrite is present in organic-rich shales of the 2.32-Gyr-old Rooihoogte and Timeball Hill formations, South Africa. The range of the isotopic composition of sulphur in this pyrite is large and shows no evidence of mass-independent fractionation, indicating that atmospheric oxygen was present at significant levels (that is, greater than 10(-5) times that of the present atmospheric level) during the deposition of these units. The presence of rounded pebbles of sideritic iron formation at the base of the Rooihoogte Formation and an extensive and thick ironstone layer consisting of haematitic pisolites and oölites in the upper Timeball Hill Formation indicate that atmospheric oxygen rose significantly, perhaps for the first time, during the deposition of the Rooihoogte and Timeball Hill formations. These units were deposited between what are probably the second and third of the three Palaeoproterozoic glacial events.

Dexmedetomidine infusion and somatosensory evoked potentials

Intraoperative neurophysiologic monitoring requires information on the effects of anesthetic drugs because these drugs can directly alter evoked potentials, thus interfering with monitoring. We report on our evaluation of the effect of the recently introduced alpha2-adrenergic agonist, dexmedetomidine, on the somatosensory evoked potentials in two patients undergoing cervico-occipital fusion. Our results suggest that, although dexmedetomidine can affect the later cortical peaks of somatosensory evoked potentials (SSEPs), consistent and reproducible potentials can be recorded.