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مقدمة الهسي-يوتشي
يتناول الكتاب تعريف دقيق بعالم الرائعة الصينية الخالدة الهسي يو-تشي أو (الرحلة إلى الغرب) ومع محاولة جادة ورصينة للكشف عن مغاليقها وأسرارها واكتناه غموضها وسبر أغوارها، يتكامل هذا كله بتحليل شائق لأبطال الرحلة إلى الغرب والعالم الخلفي الذي نبعوا منه والأهداف التي سعوا إلى تحقيقها من وراء رحلتهم العجيبة وما انتهى إليه مصير كل منهم في ختمها، باستثناء كتاب واحد يحمل عنوان جبل اللهب صادر في بكين، فإن هذا الكتاب الماثل بين يدي القارئ يعد المحاولة الأخيرة لتقديم الهسي يوسوليو تشي للقارئ العربي بلغة الضاد.
BOOK
Northern peatland carbon stocks and dynamics: a review
Peatlands contain a large belowground carbon (C) stock in the biosphere, and their dynamics have important implications for the global carbon cycle. However, there are still large uncertainties in C stock estimates and poor understanding of C dynamics across timescales. Here I review different approaches and associated uncertainties of C stock estimates in the literature, and on the basis of the literature review my best estimate of C stocks and uncertainty is 500 ± 100 (approximate range) gigatons of C (Gt C) in northern peatlands. The greatest source of uncertainty for all the approaches is the lack or insufficient representation of data, including depth, bulk density and carbon accumulation data, especially from the world's large peatlands. Several ways to improve estimates of peat carbon stocks are also discussed in this paper, including the estimates of C stocks by regions and further utilizations of widely available basal peat ages. Changes in peatland carbon stocks over time, estimated using Sphagnum (peat moss) spore data and down-core peat accumulation records, show different patterns during the Holocene, and I argue that spore-based approach underestimates the abundance of peatlands in their early histories. Considering long-term peat decomposition using peat accumulation data allows estimates of net carbon sequestration rates by peatlands, or net (ecosystem) carbon balance (NECB), which indicates more than half of peat carbon (> 270 Gt C) was sequestrated before 7000 yr ago during the Holocene. Contemporary carbon flux studies at 5 peatland sites show much larger NECB during the last decade (32 ± 7.8 (S.E.) g C m−2 yr–1) than during the last 7000 yr (∼ 11 g C m−2 yr–1), as modeled from peat records across northern peatlands. This discrepancy highlights the urgent need for carbon accumulation data and process understanding, especially at decadal and centennial timescales, that would bridge current knowledge gaps and facilitate comparisons of NECB across all timescales.
Journal Article
Illuminating gravitational waves
Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.
Journal Article
Photocatalytic toluene oxidation with nickel-mediated cascaded active units over Ni/Bi2WO6 monolayers
Adsorption and activation of C–H bonds by photocatalysts are crucial for the efficient conversion of C–H bonds to produce high-value chemicals. Nevertheless, the delivery of surface-active oxygen species for C–H bond oxygenation inevitably needs to overcome obstacles due to the separated active centers, which suppresses the catalytic efficiency. Herein, Ni dopants are introduced into a monolayer Bi
2
WO
6
to create cascaded active units consisting of unsaturated W atoms and Bi/O frustrated Lewis pairs. Experimental characterizations and density functional theory calculations reveal that these special sites can establish an efficient and controllable C–H bond oxidation process. The activated oxygen species on unsaturated W are readily transferred to the Bi/O sites for C–H bond oxygenation. The catalyst with a Ni mass fraction of 1.8% exhibits excellent toluene conversion rates and high selectivity towards benzaldehyde. This study presents a fascinating strategy for toluene oxidation through the design of efficient cascaded active units.
By introducing Ni dopants into monolayer Bi
2
WO
6
, Bi/O frustrated Lewis pairs, unsaturated W atoms, and Ni active units are formed. The authors show that these units facilitate oxygen species transfer and enhance photocatalytic toluene oxidation.
Journal Article
Handbook of phonological theory
In a series of essays on topics as varied as underspecification theory, prosodic morphology, and syllable structure, 38 leading phonologists offer a critical survey of the leading and guiding ideas that lie behind the research in this active area of linguistic research.
Book
Basal forebrain cholinergic input mediates adaptive attention allocation to enhance olfactory discrimination
By selectively amplifying relevant sensory input, animals efficiently allocate limited cognitive resources to improve decision-making. Allocation of attention is aligned with behavioral goals and adaptive to cognitive demand, but the circuit mechanisms remain unclear. Here, we identify an attention circuit for odor processing where cholinergic neurons in the horizontal nucleus of the diagonal band provide top–down control through inhibitory dopaminergic short-axon cells in the mouse olfactory bulb. Attentional cue triggered cholinergic activity provides preparatory disinhibition of olfactory sensory axons to enhance response to reward-associated odors and improves decision-making. Preparatory, but not reward-dependent, cholinergic activity is disengaged in proficient animals when the task becomes routine, underlying a trade-off between proficiency and attention engagement. Direct manipulation of the disinhibitory circuit reinstates attentional effect without eliciting general arousal. A computational model of the circuit recapitulates the dynamic change in attention responses and illustrates a two-stage adaptation that efficiently allocates cognitive resources.
Journal Article
Electrochemical generation of hydrogen peroxide from a zinc gallium oxide anode with dual active sites
Electrochemical water oxidation enables the conversion of H
2
O to H
2
O
2
. It holds distinct advantages to the O
2
reduction reaction, which is restricted by the inefficient mass transfer and limited solubility of O
2
in aqueous media. Nonetheless, most reported anodes suffer from high overpotentials (usually >1000 mV) and low selectivity. Electrolysis at high overpotentials often causes serious decomposition of peroxides and leads to declined selectivity. Herein, we report a ZnGa
2
O
4
anode with dual active sites to improve the selectivity and resist the decomposition of peroxides. Its faradaic efficiency reaches 82% at 2.3 V versus RHE for H
2
O
2
generation through both direct (via OH
−
) and indirect (via HCO
3
−
) pathways. The percarbonate is the critical species generated through the conversion of bicarbonate at Ga-Ga dual sites. The peroxy bond is stable on the surface of the ZnGa
2
O
4
anode, significantly improving faradaic efficiency.
Developing efficient anodes for H
2
O
2
production via water oxidation remains challenging. Here, the authors report a ZnGa
2
O
4
anode with dual active sites to improve the selectivity and to resist the decomposition of H
2
O
2
, and the peak faradaic efficiency reaches 82% at a low potential.
Journal Article
Circulating levels of leptin, adiposity and breast cancer risk
The present case–control study was to investigate the relationships of plasma leptin level and anthropometric measures of adiposity with the risk of breast cancer. Questionnaire information, anthropometric measures and blood samples were taken before treatment from 297 incident cases with breast cancer and 593 controls admitted for health examination at the Tri-Service General Hospital, Taipei, between 2004 and 2006. Plasma levels of leptin were measured by RIA. Logistic regression analysis was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for assessing the associations. Overall, higher leptin concentrations were significantly associated with an increased risk of breast cancer (OR (95% CI) for top
vs
bottom tertile of leptin was 1.63 (1.07–2.49),
P
trend
=0.009). Waist circumference was a significant anthropometric factor for breast cancer in both pre- and postmenopausal women. Furthermore, the associations of leptin with breast cancer risk remained after adjustment for obesity indices. These results suggest that leptin may have an independent role in breast tumorigenesis. Regardless of the impact of circulating leptin, more research is needed to elucidate molecular mechanisms and local leptin levels that are critical for the development of breast cancers.
Journal Article