Energy Injection Episodes in Gamma Ray Bursts: The Light Curves and Polarization Properties of GRB 021004

Several GRB afterglow light curves deviate strongly from the power law decay observed in most bursts. We show that these variations can be accounted for by including refreshed shocks in the standard fireball model previously used to interpret the overall afterglow behavior. As an example we consider GRB 021004 that exhibited strong light curve variations and has a reasonably well time-resolved polarimetry. We show that the light curves in the R-band, X-rays and in the radio can be accounted for by four energy injection episodes in addition to the initial event. The polarization variations are shown to be a consequence of the injections.Comment: 4 pages, 2 figures. To appear in ApJ

The relationship of gastrointestinal symptoms and menstrual cycle phase in young healthy women

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenBACKGROUND: Abdominal discomfort is a common complaint by women and may vary with the menstrual cycle. The aim of this study was to investigate abdominal symptoms and general well being of women in relation to different phases of the menstrual cycle as well as gastrointestinal transit time. METHODS: Fourteen young women who were not using any contraceptive medications were recruited. Questionnaire was used to exclude functional gastrointestinal problems. Questionnaires on abdominal symptoms and general well being were used. Gastric emptying time, small intestinal transit time and colonic transit time were measured and serum sex hormone concentrations were measured at three points in the menstrual cycle. RESULTS: Abdominal symptoms were significantly more pronounced at the beginning of the follicular phase. Gastric emptying and colonic transit times were not significantly different between the follicular and the luteal phase of the menstrual cycle. Small bowel transit was faster in the luteal phase (75,7 min) compared with the follicular phase (99,3 min). There was no correlation between the transit times, symptoms or hormone concentrations. CONCLUSIONS: Results indicate that women experience more abdominal symptoms at the beginning of the follicular phase compared to the early luteal phase. Small bowel transit appears to be faster in the luteal phase than in the follicular phase. Further studies on the relationship of gastrointestinal symptoms and the menstrual cycle are needed.Bakgrunnur: Meltingarfæraeinkenni eru algeng hjá konum og geta verið breytileg í tíðahringnum. Markmið þessarar rannsóknar var að kanna meltingarfæraeinkenni og almenna andlega líðan kvenna í tengslum við mismunandi hluta tíðahringsins auk flæðitíma um meltingarveg. Aðferðir: Fjórtán ungar konur sem ekki notuðu getnaðarvarnarlyf tóku þátt í rannsókninni. Spurningalisti var notaður til að útiloka starfræna kvilla frá meltingarvegi. Þátttakendur svöruðu spurningum um einkenni frá meltingarvegi og almenna líðan. Magatæmingarhraði, flæðishraði um mjógirni og flæðishraði um ristil var mældur auk styrks kynhormóna í blóði. Niðurstöður: Meltingarfæraeinkenni voru marktækt meiri í eggbúsfasa en gulbúsfasa en ekki fannst munur á andlegri líðan tengdur hlutum tíðahrings. Ekki var marktækur munur á magatæmingarhraða og flæðishraða um ristil milli eggbús- og gulbúsfasa tíðahringsins. Flæði um mjó-girni var hraðara í gulbúsfasa (75,7 mínútur) en í eggbúsfasa (99,3 mínútur). Engin tengsl fundust milli flæðishraða, einkenna og styrks kynhormóna í blóði. Ályktanir: Konur virðast hafa meiri meltingarfæraeinkenni í upphafi eggbúsfasa en í fyrri hluta gulbúsfasa. Flæðishraði um mjógirni kann að vera meiri í gulbúsfasa en í eggbúsfasa. Þörf er á frekari rannsóknum á meltingarfæraeinkennum kvenna í tengslum við hluta tíðahrings og flæðishraða um meltingarveg

Effects of bioaugmentation by an anaerobic lipolytic bacterium on anaerobic digestion of lipid-rich waste

The effect of bioaugmentation with an anaerobic lipolytic bacterial strain on the anaerobic digestion of restaurant lipid-rich waste was studied in batch experiments with a model waste containing 10% lipids (triolein) under two sets of experimental conditions: (A) methanogenic conditions, and (B) initially acidogenic conditions in the presence of only the lipolytic strain biomass (4 days), followed by methanogenic conditions. The bioaugmenting lipolytic strain, Clostridium lundense (DSM 17049T), was isolated from bovine rumen. The highest lipolytic activity was detected at the beginning of the experiments. A higher methane production rate, 27.7 cm3 CH4(STP) g-1 VSadded day-1 (VS, volatile solids) was observed in experiment A with the presence of the bioaugmenting lipolytic strain under methanogenic conditions. The highest initial oleate concentration, 99% of the total oleate contained in the substrate, was observed in the experiments with the bioaugmenting lipolytic strain under treatment A conditions; the levels of palmitate and stearate were also higher until day 15, indicating that the bioaugmentation strategy improved the hydrolysis of the lipid fraction. In general, the results indicated that degradation of the long chain fatty acids (LCFAs) controlled the digestion process.Swedish Energy Agency ; Fundação para a Ciência e a Tecnologia (FCT

Performance of a sisal fibre fixed-bed anaerobic digester for biogas production from sisal pulp waste

A single stage anaerobic digester employing a sisal fibre waste fixed bed was studied for biogas production from sisal pulp waste. The fibre was colonized by microorganisms involved in biogas production. The sisal pulp waste to be digested was fed from the top and was sprinkled intermittently with recirculating leachate from the material. Organic loading rates of 0.1-10 kg volatile solids (VS) m-3d-1 could be applied and methane yields in the range of 0.13-0.48 m3 CH4 kg-1 VS added were obtained. The average methane content in the biogas produced from sisal pulp waste was 55%, and the biogas production rate was 0.15-0.54 m3m-3d-1. The methane yield obtained and the highest organic loading rate that could be sustained by this simple, fixed-bed digester are indications of an attractive system in terms of performance and reliability. It is concluded that the sisal fibre waste fixed bed is a promising carrier for microbes and can be employed for long-term operation without changing the bed. Tanzania Journal of Science Vol. 31 (2) 2005: pp. 41-5

Influence of lipid concentration on the hydrolysis and biomethanation of lipid rich wastes

The influence of lipid concentration on hydrolysis and biomethanation of an artificial lipid rich (triolein) waste was evaluated. No inhibition on methane production was observed for tests with 5, 10 and 18 % (w/w, based on COD) of lipid. For higher amounts of lipid (31, 40 and 47 %) inhibition was observed. However, the process was able to recover from the inhibition. When the effect of lipase addition on enzymatic hydrolysis of lipids was studied, results showed that the higher the enzyme concentration, the more accentuated was the inhibition of the methane production. The enzyme seems to enhance the hydrolysis and produced intermediates are causing inhibition of the later steps of the degradation process. Since the VFA profiles presented similar trends for the different lipid amounts tested, the major obstacle to methane production is believed to be the LCFA formed.Fundação para a Ciência e a Tecnologia (FCT).The Swedish Energy Agency

Anaerobic digestion of lipid-rich waste : effects of lipid concentration

The influence of lipid concentration on hydrolysis and biomethanation of a lipid-rich (triolein) model waste was evaluated in batch. The effect of increasing the concentration of lipid from 5% to 47% (w/w), based on chemical oxygen demand (COD), was investigated. The methane recovery observed was above 93% for all tests. An initial lag phase of approximately 6–10 days was observed for all tests. The methane production rate observed was similar for tests with 5%, 10% and 18% lipid (w/w, COD basis). For higher amounts of lipid (31%, 40% and 47%), a stronger inhibition was observed. However, the process was able to recover from the inhibition. When the effect of addition of lipase on enzymatic hydrolysis of lipids was studied, the results showed that the higher the enzyme concentration, the more accentuated was the inhibition of methane production. The enzyme appears to enhance the hydrolysis but the intermediates produced caused inhibition of the later steps in the degradation process. Since the volatile fatty acid (VFA) profiles presented similar trends for the different concentrations of lipid tested, the major obstacle to methane production was the long-chain fatty acids (LCFA) formation.Swedish Energy AgencyFundação para a Ciência e a Tecnologia (FCT

HST/STIS Imaging of the Host Galaxy of GRB980425/SN1998bw

We present HST/STIS observations of ESO 184-G82, the host galaxy of the gamma-ray burst GRB 980425 associated with the peculiar Type Ic supernova SN1998bw. ESO 184-G82 is found to be an actively star forming SBc sub-luminous galaxy. We detect an object consistent with being a point source within the astrometric uncertainty of 0.018 arcseconds of the position of the supernova. The object is located inside a star-forming region and is at least one magnitude brighter than expected for the supernova based on a simple radioactive decay model. This implies either a significant flattening of the light curve or a contribution from an underlying star cluster.Comment: 12 pages, 2 figures, AASTeX v5.02 accepted for publication in ApJ Letter

Associating Liver Partition and Portal Vein Ligation for Staged Hepatectomy (ALPPS) procedure for colorectal liver metastasis

Since first described, Associating Liver Partition and Portal Vein Ligation for Staged Hepatectomy (ALPPS) has garnered boisterous praise and fervent criticism. Its rapid adoption and employment for a variety of indications resulted in high perioperative morbidity and mortality. However recent risk stratification, refinement of technique to reduce the impact of stage I and progression along the learning curve have resulted in improved outcomes. The first randomized trial comparing ALPPS to two stage hepatectomy (TSH) for colorectal liver metastases (CRLM) was recently published demonstrating comparable perioperative morbidity and mortality with improved resectability and survival following ALPPS. In this review, as ALPPS enters the thirteenth year since conception, the current status of this contentious two stage technique is presented and best practices for deployment in the treatment of CRLM is codified

Using stable isotopes and continuous meltwater river monitoring to investigate the hydrology of a rapidly retreating Icelandic outlet glacier

Virkisjökull is a rapidly retreating outlet glacier draining the western flanks of Öræfajökull in SE Iceland. Since 2011 there have been continuous measurements of flow in the proglacial meltwater channel and regular campaigns to sample stable isotopes δ2H and δ18O from the river, ice, moraine springs and groundwater. The stable isotopes provide reliable end members for glacial ice and shallow groundwater. Analysis of data from 2011 to 2014 indicates that although ice and snowmelt dominate summer riverflow (mean 5.3–7.9 m3 s−1), significant flow is also observed in winter (mean 1.6–2.4 m3 s−1) due primarily to ongoing glacier icemelt. The stable isotope data demonstrate that the influence of groundwater discharge from moraines and the sandur aquifer increases during winter and forms a small (15–20%) consistent source of baseflow to the river. The similarity of hydrological response across seasons reflects a highly efficient glacial drainage system, which makes use of a series of permanent englacial channels within active and buried ice throughout the year. The study has shown that the development of an efficient year round drainage network within the lower part of the glacier has been coincident with the stagnation and subsequent rapid retreat of the glacier

Upper limit on spontaneous supercurrents in Sr2_2RuO4_4

It is widely believed that the perovskite Sr$_2$RuO$_4$ is an unconventional superconductor with broken time reversal symmetry. It has been predicted that superconductors with broken time reversal symmetry should have spontaneously generated supercurrents at edges and domain walls. We have done careful imaging of the magnetic fields above Sr$_2$RuO$_4$ single crystals using scanning Hall bar and SQUID microscopies, and see no evidence for such spontaneously generated supercurrents. We use the results from our magnetic imaging to place upper limits on the spontaneously generated supercurrents at edges and domain walls as a function of domain size. For a single domain, this upper limit is below the predicted signal by two orders of magnitude. We speculate on the causes and implications of the lack of large spontaneous supercurrents in this very interesting superconducting system.Comment: 9 page