Chlorophyll and pheophytin protonated and deprotonated ions: Observation and theory.

Pheophytin a and chlorophyll a have been investigated by electrospray mass spectrometry in the positive and negative modes, in view of the importance of the knowledge of their properties in photosynthesis. Pheophytin and chlorophyll are both observed intensely in the protonated mode, and their main fragmentation route is the loss of their phytyl chain. Pheophytin is observed intact in the negative mode, while under collisions, it is primarily cleaved beyond the phytyl chain and loses the attaching propionate group. Chlorophyll is not detected in normal conditions in the negative mode, but addition of methanol solvent molecule is detected. Fragmentation of this adduct primarily forms a product (-30 amu) that dissociates into dephytyllated deprotonated chlorophyll. Semi-empirical molecular dynamics calculations show that the phytyl chain is unfolded from the chlorin cycle in pheophytin a and folded in chlorophyll a. Density functional theory calculations have been conducted to locate the charges on protonated and deprotonated pheophytin a and chlorophyll a and have found the major location sites that are notably more stable in energy by more than 0.5 eV than the others. The deprotonation site is found identical for pheophytin a and the chlorophyll a-methanol adduct. This is in line with experiment and calculation locating the addition of methanol on a double bond of deprotonated chlorophyll a.

Enhancing Ultradeep Hydrodesulfurization of Coker Diesel through Adsorptive Predenitrogenation.

The petroleum refining industry places significant challenge in the production of ultralow-sulfur diesel (ULSD) from various middle distillates with high nitrogen concentration in an energy-efficient and cost-effective way to meet strict environmental regulations as coexisting nitrogen compounds significantly inhibit the ultradeep hydrodesulfurization (HDS). Among all of the approaches reported in the literature for this challenge, a combination of adsorptive denitrogenation (ADN) and HDS has attracted great attention. This study focuses on ultradeep HDS of coker diesel (CD) through a synergistic approach combining ADN over a carbon-based adsorbent and the current HDS process. The study found that the predenitrogenation significantly enhanced the HDS reactivity of CD and greatly reduced the start of run temperature for producing ULSD by even 20 °C, depending on the denitrogenation depth. It results in dominantly decreasing energy and H2 consumption in the HDS process, and increasing the lifetime of the catalyst. Furthermore, the predenitrogenation prior to HDS significantly improved the quality of the hydrodesulfurized product by decreasing aromatic content and density, increasing the cetane index, and improving the color and stability of the product as the HDS process for producing ULSD can be conducted at a much lower temperature. The study demonstrated the combination of ADN and HDS for producing ULSD from CD on a pilot unit scale, and the advantages and disadvantages of this combination were discussed in comparison with the conventional HDS process. In addition, it was found that there is a good linear relationship between the logarithm of the product sulfur concentration and the HDS reaction temperature, which can be used conveniently to predict the start-of-run temperature to achieve different sulfur levels.

Perinatal outcome of vaginally delivered twin gestations with a larger twin B.

OBJECTIVE: To study the perinatal outcome of vaginally delivered twins when twin B is more than 250 g larger than twin A. STUDY DESIGN: Maternal and neonatal charts of live-born, nonanomalous twins, >25 weeks' gestation and vaginally delivered over a period of 17 years were reviewed. The results of this review were distributed among two groups: (1). those with twin B more than 250 g larger than twin A (DeltaBW>250) and (2). those where the difference was <250 g (DeltaBW<250). For vaginally delivered twin gestations, the perinatal outcome of twin B in the group DeltaBW>250 was compared to that of its co-twin, and to that of twin B in the group DeltaBW<250. RESULTS: Of the 679 twin gestations reviewed, 138 (20.6%) were in the group DeltaBW>250, of whom 73 (52.9%) delivered vaginally despite malpresentation in 39.7%. The vaginally delivered twin pregnancies in the groups DeltaBW>250 (n=73) and DeltaBW<250 (n=303) had similar demographics, parity, presentation, gestational age at delivery, and duration of the first stage of labor. Discordant twins were more frequent in the group DeltaBW>250 (26.0 versus 9.5%, p=0.001). Twin B in the group DeltaBW<250 was smaller, with higher incidence of growth restriction, low 5 min Apgar score, and hyperbilirubinemia compared to twin B in the group DeltaBW>250. There was no difference in the incidence of intraventricular hemorrhage, seizures, sepsis, neonatal death, and median nursery stay. Except for a lower median Apgar score at 1 min in twin B and a longer median nursery stay in twin A, twins A and B in the group DeltaBW>250 were similar regarding all other neonatal outcome variables. CONCLUSIONS: When twin B is more than 250 g larger than A, and both are delivered vaginally, the perinatal outcome is similar to its co-twin as well as to that of twin B of all other vaginally delivered twins. That twin B is larger than A is not itself a contraindication to attempted vaginal delivery.

Lateral distribution of endometriomas as a function of age.

The lateral asymmetry of ovarian endometriomas, with a left-sided predilection, seems to disappear with advancing age. This asymmetry does not seem to persist in women >35 years of age.

Impact of advanced maternal age on pregnancy outcome.

The aim of this study was to compare the pregnancy outcome and delivery complications in women 40 years or older (cases) to that of women 20 to 30 years old (controls). Over a 5-year period, 319 cases had a singleton delivery in our institution. These women were compared with 326 controls. Parity was significantly higher in cases compared with controls (3.2 vs. 1.8). Advanced maternal age, compared with younger age, was associated with significantly higher rates of preterm delivery (16.0 vs. 8.0%), cesarean delivery (CS) (31.3 vs. 13.5%), and the occurrence of one or more antepartum complications (29.5 vs. 16.6%). When the two groups were subdivided according to parity, rates of preterm delivery, CS, preeclampsia, gestational diabetes, chronic hypertension, and labor induction were each significantly higher among older multiparas compared with control multiparas. However, only preterm delivery, CS rates, and uterine fibroids were found to be significantly higher in older nulliparous compared with young nulliparous women. We conclude that multiparous women at least 40 years old have a higher antepartum complication rate including intrauterine fetal death compared with younger women.

Neonatal outcome of growth discordant twin gestations.

The aim of the study was to compare a variety of neonatal outcome variables of growth concordant twin gestations (CT) to that of growth discordant twins (DT). Maternal and neonatal charts of live, non-anomalous twins > 25 weeks' gestation from 1984-2000 with no evidence of twin-twin transfusion syndrome were reviewed for several variables. DT occurred in (N = 81) 11.9% of all twin pregnancies. In 61.7% of DT, twin B was the smaller of the twins. There was no difference in maternal age, admission indications, or antepartum complications between both groups. DT had a significantly higher incidence of growth restriction compared to CT (88.9% vs 43.5%, p < 0.001). More mothers of DT required oxytocin (37.0% vs 26.3%, p = 0.024); however, cesarean delivery rate and indications were similar in both groups. A similar percentage of infants had AS < 4 at 1 min and AS < 7 at 5 min in both groups. There was no difference between the 2 groups in neonatal complications including: trauma, respiratory distress syndrome, intraventricular hemorrhage, necrotizing enterocolitis, pneumonia, seizures, or neonatal mortality. However, DT had a significantly higher incidence of hyperbilirubinemia, need for mechanical ventilation and a longer nursery stay. The neonatal outcome of growth discordant twins is worse than that of concordant twins even in pregnancies uncomplicated by twin-twin transfusion syndrome or congenital anomalies.

Bone mineralization in newborns whose mothers received magnesium sulphate for tocolysis of premature labour.

Prolonged maternal magnesium sulphate infusion therapy for tocolysis of premature labour may result in secondary fetal hypermagnesaemia, which has been associated with bony abnormalities in the newborn. We report on four infants, members of two twin pregnancies, who were exposed to prolonged fetal hypermagnesaemia. Three of the infants, all appropriate for gestational age, showed abnormal radiological findings consisting of abnormal mineralisation of long-bone metaphyses owing to fetal hypermagnesaemia. The fourth infant, who was growth retarded, had normal bones. Intrauterine growth restriction appears to be protective against magnesium sulphate-induced abnormal bone mineralisation in the newborn.