Elementary excitations in entangled states such as quantum spin liquids may exhibit exotic statistics different from those obeyed by fundamental bosons and fermions. Non-Abelian anyons exist in a ...Kitaev spin liquid-the ground state of an exactly solvable model. A smoking-gun signature of these excitations, namely a half-integer quantized thermal Hall conductivity, was recently reported in α-RuCl
. While fascinating, a microscopic theory for this phenomenon remains elusive because the pure Kitaev model cannot display this effect in an intermediate magnetic field. Here we present a microscopic theory of the Kitaev spin liquid emerging between the low- and high-field states. Essential to this result is an antiferromagnetic off-diagonal symmetric interaction which allows the Kitaev spin liquid to protrude from the ferromagnetic Kitaev limit under a magnetic field. This generic model displays a strong field anisotropy, and we predict a wide spin liquid regime when the field is perpendicular to the honeycomb plane.
The 3′ end of the 18S ribosomal RNA is formed by the endoribonuclease Nob1. How cells ensure the accuracy of the 3′ end has remained a mystery. A new study in PLOS Biology revealed that there are ...multiple checkpoints to ensure that only ribosomes containing the correct 3′ end participate in translation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
To study the behavior of Drosophila, it is often necessary to restrain and mount individual flies. This requires removal from food, additional handling, anesthesia, and physical restraint. We find a ...strong positive correlation between the length of time flies are mounted and their subsequent reflexive feeding response, where one hour of mounting is the approximate motivational equivalent to ten hours of fasting. In an attempt to explain this correlation, we rule out anesthesia side-effects, handling, additional fasting, and desiccation. We use respirometric and metabolic techniques coupled with behavioral video scoring to assess energy expenditure in mounted and free flies. We isolate a specific behavior capable of exerting large amounts of energy in mounted flies and identify it as an attempt to escape from restraint. We present a model where physical restraint leads to elevated activity and subsequent faster nutrient storage depletion among mounted flies. This ultimately further accelerates starvation and thus increases reflexive feeding response. In addition, we show that the consequences of the physical restraint profoundly alter aerobic activity, energy depletion, taste, and feeding behavior, and suggest that careful consideration is given to the time-sensitive nature of these highly significant effects when conducting behavioral, physiological or imaging experiments that require immobilization.
The bond-dependent Kitaev model on the honeycomb lattice with anyonic excitations has recently attracted considerable attention. However, in solid-state materials other spin interactions are present, ...and among such additional interactions, the off-diagonal symmetric Gamma interaction, another type of bond-dependent term, has been particularly challenging to fully understand. A minimal Kitaev-Gamma model has been investigated by various numerical techniques under a magnetic field, but definite conclusions about field-induced spin liquids remain elusive. One reason for this may lie in the limited sizes of the two-dimensional geometry it is possible to access numerically, and missed incommensurately ordered states may be interpreted as a spin liquid. Here we focus on the Kitaev-Gamma ladder model as a guide to the phase space of disordered states which could potentially become a spin liquid in the two-dimensional limit. We determine the entire phase diagram in the presence of a magnetic field along the 111 direction. Because of the competition between the interactions and the field, an extremely rich phase diagram emerges with 15 distinct phases. Focusing near the antiferromagnetic Kitaev region, we identify nine different phases solely within this region: several incommensurate magnetically ordered phases, spin-nematic, and two chiral phases with enhanced entanglement. Of particular interest is a highly entangled phase with staggered chirality with zero-net flux occurring at intermediate field, which along with its companion phases outlines a heart-shaped region of high entanglement, the heart of entanglement. We compare our results for the ladder with aC3symmetric cluster of the two-dimensional honeycomb lattice, and offer insight into possible spin liquids in the two-dimensional limit.
Due to their high stability towards enzymatic hydrolysis C‐acyl glycosidic compounds are useful synthetic intermediates for potential candidates in drug discovery. Syntheses for C‐acyl mannosides ...have remained scarce and usually employ donors obtained from lengthy syntheses. Furthermore, syntheses of unprotected C‐acyl mannosides have not been reported so far, due to the incapability of the C‐acyl mannoside motif with deprotection conditions for protective groups commonly used in carbohydrate chemistry. Herein, we report an efficient and highly α‐selective four‐step one‐pot method for the synthesis of C‐acyl α‐d‐manno‐, l‐rhamno‐ and d‐lyxopyranosides from easily accessible persilylated monosaccharides and dithianes requiring only trace amounts of a copper source as catalyst and explain the crucial role of the catalyst by mechanistic studies. Furthermore, the C‐acyl α‐glycosides were easily isomerized to give rapid access to their β‐anomers.
Just a pinch of copper iodide promotes the reaction of manno‐type glycosyl iodides with lithiated dithianes. Herein, we report an efficient and highly α‐selective four‐step one‐pot method for the synthesis of unprotected manno‐type C‐acyl pyranosides. The crucial role of the catalyst was proven by mechanistic studies and DFT calculations, suggesting a copper‐radical mechanism over a SN‐type mechanism.
This book examines the impact of "out of Africa" migrations on the development of the Global North. The current body of research on the history of human migrations has documented the African global ...presence from ancient times to the present. Yet the impact of the African migrations, voluntary or forced, on the development of the Modern World, especially the Global North, has either been neglected, ignored or distorted in historical accounts. It is now common knowledge that Africa has most of the world's natural resources, primarily for exports. These resources include gold, diamond, copper, oil and natural gas, iron ore, aluminum, uranium, phosphate, etc. It is equally important to note that available data have also documented Africa's exports of its human capital for the development of the modern world, especially the Global North. In filling this gap in the literature, this volume focuses on the United States of America, the most powerful nation in the Global North, for an in-depth study. It is hypothesized in this study that Africans and peoples of African descent were central to the development and growth of the United States from its beginnings to the present. The study depends primarily on culturally relevant Historiographical method. A major distinguished feature of this volume is its Afrocentric multidisciplinary approach while relying heavily on the discipline of History. The concluding chapter draws on multiple sources in summarizing the contributions and the impact of Africa and peoples of African descent in the American Experience as a major part of the Global North. It probes current trends and trajectories in African American Studies; African American Quality of Life; the future role of Africa and the African Diaspora in American life and the Global North.
Baboons inform on human gut microbiota
Commensal bacteria are found throughout an organism, but it is not known whether associations between gut bacteria and their host are heritable. Grieneisen
et ...al.
examined changes in the microbiomes of 585 wild baboons from fecal samples collected over 14 years (see the Perspective by Cortes-Ortiz and Amato). Almost all microbiome traits tested demonstrated some level of statistically significant heritability. Most heritability values were low but varied over time correlating with the age of the host. Baboons live in an environment similar to that postulated for early humans and have a microbiome similar to that of humans. Thus, this heritability of the microbiome may reflect similar genetic determinants in humans, for which similar datasets are not available.
Science
, aba5483, this issue p.
181
; see also abj5287, p.
159
The baboon gut microbiome is heritable but changes over time.
Relatives have more similar gut microbiomes than nonrelatives, but the degree to which this similarity results from shared genotypes versus shared environments has been controversial. Here, we leveraged 16,234 gut microbiome profiles, collected over 14 years from 585 wild baboons, to reveal that host genetic effects on the gut microbiome are nearly universal. Controlling for diet, age, and socioecological variation, 97% of microbiome phenotypes were significantly heritable, including several reported as heritable in humans. Heritability was typically low (mean = 0.068) but was systematically greater in the dry season, with low diet diversity, and in older hosts. We show that longitudinal profiles and large sample sizes are crucial to quantifying microbiome heritability, and indicate scope for selection on microbiome characteristics as a host phenotype.
Purpose The purpose of this case study was to complement existing weeding and retention criteria beyond the most used methods in academic libraries and to consider citation counts in the ...identification of important scholarly works. Design/methodology/approach Using a small sample of items chosen for withdrawal from a small liberal arts college library, this case study looks at the use of Google Scholar citation counts as a metric for identification of notable monographs in the social sciences and mathematics. Findings Google Scholar citation counts are a quick indicator of classic, foundational or discursive monographs in a particular field and should be given more consideration in weeding and retention analysis decisions that impact scholarly collections. Higher citation counts can be an indicator of higher circulation counts. Originality/value The authors found little indication in the literature that Google Scholar citation counts are being used as a metric for identification of notable works or for retention of monographs in academic libraries.
A man in his 60s was admitted to our institution for workup of newly diagnosed ischemic heart disease. This was on the background of recent hospital admission with Salmonella typhimurium bacteraemia ...of unknown source. During his admission the patient developed progressively worsening left leg pain. Duplex US demonstrated a below knee DVT, however subsequent triple phase CT revealed a ruptured mycotic popliteal artery aneurysm. The patient was transferred for emergent superficial femoral artery to below knee popliteal artery bypass graft using the reversed contralateral greater saphenous vein with associated aneurysmectomy. The patient went on to make a successful recovery. Mycotic aneurysms involving Salmonella species have been documented in the abdominal aorta; however, remain a rare occurrence in popliteal arteries1. Cross sectional arterial imaging is recommended when there is suspicion of peripheral arterial bacterial seeding, in order to accurately capture mycotic aneurysms. This case highlights the importance of having a low threshold for arterial imaging in a patient with a history of Salmonella bacteraemia and acute limb pain.
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