Energy considerations for a superlens based on metal/dielectric multilayers

We investigate the resolution and absorption losses of a Ag/GaP multilayer superlens. For a fixed source to image distance the resolution is independent of the position of the lens but the losses depend strongly on the lens placement. The absorption losses associated with the evanescent waves can be significantly larger than losses associated with the propagating waves especially when the superlens is close to the source. The interpretation of transmittance values greater than unity for evanescent waves is clarified with respect to the associated absorption losses.Comment: to be published in Optics Expres

The effects of caloric restriction on adipose tissue and metabolic health are sex- and age-dependent

Caloric restriction (CR) is a nutritional intervention that reduces the risk of age-related diseases in numerous species, including humans. CR's metabolic effects, including decreased fat mass and improved insulin sensitivity, play an important role in its broader health benefits. However, the extent and basis of sex differences in CR's health benefits are unknown. We found that 30% CR in young (3-month-old) male mice decreased fat mass and improved glucose tolerance and insulin sensitivity, whereas these effects were blunted or absent in young female mice. Females' resistance to fat and weight loss was associated with decreased lipolysis, lower systemic energy expenditure and fatty acid oxidation, and increased postprandial lipogenesis compared to males. Positron emission tomography-computed tomography (PET/CT) with 18F-fluorodeoxyglucose (18F-FDG) showed that peripheral glucose uptake was comparable between sexes. Instead, the sex differences in glucose homeostasis were associated with altered hepatic ceramide content and substrate metabolism: compared to CR males, CR females had lower TCA cycle activity but higher blood ketone concentrations, a marker of hepatic acetyl-CoA content. This suggests that males use hepatic acetyl-CoA for the TCA cycle whereas in females it accumulates, thereby stimulating gluconeogenesis and limiting hypoglycaemia during CR. In aged mice (18-months old), when females are anoestrus, CR decreased fat mass and improved glucose homeostasis to a similar extent in both sexes. Finally, in a cohort of overweight and obese humans CR-induced fat loss was also sex- and age-dependent: younger females (<45 years) resisted fat loss compared to younger males while in older subjects (>45 years) this sex difference was absent. Collectively, these studies identify age-dependent sex differences in the metabolic effects of CR and highlight adipose tissue, the liver and oestrogen as key determinants of CR's metabolic benefits. These findings have important implications for understanding the interplay between diet and health and for maximising the benefits of CR in humans

The regulation of haematopoietic niche: is there a role for Bone Marrow Adipocytes?

Il midollo osseo (BM) è un microambiente altamente specializzato che fornisce supporto trofico e strutturale attraverso le sue componenti stromali alle cellule staminali emopoietiche (HSC). Gli adipociti midollari (BM-A) costituiscono la componente stromale più abbondante nella nicchia, tuttavia il loro ruolo nella regolazione dell’emopoiesi non è stato ancora ben definito. È stato tuttavia dimostrato che durante la CR avviene un’espansione del tessuto adiposo midollare, responsabile a sua volta di aumentati livelli di Adiponectina (APN) sierica circolante, un ormone potenzialmente coinvolto nella regolazione dell’emopoiesi. Gli scopi di questo lavoro sono stati quelli di caratterizzare i BM-A dal punto di vista funzionale e molecolare e di determinare se l’APN possa svolgere un ruolo nella regolazione delle HSC durante la CR. A questo scopo è stata effettuata un’analisi microarray su BM-A isolati da pazienti che si sottoponevano a chirurgia dell’anca, mentre la caratterizzazione funzionale è stata effettuata tramite co-cultura con HSC. Il ruolo dell’APN è stato studiato utilizzando un modello murino APN-/- e valutando i cambiamenti nelle HSC e nelle cellule ematopoietiche circolanti in topi sottoposti a CR. I dati molecolari hanno mostrato che i BM-A hanno uno specifico pattern di espressione genica diverso dagli adipociti sottocutanei e lo studio funzionale ha dimostrato che essi sono capaci di sostenere la sopravvivenza e la differenziazione delle HSC in coltura. Lo studio dei topi APN-/- ha inoltre mostrato che in condizioni di CR l’APN svolge un ruolo nella regolazione della granulopoiesi e della linfopoiesi, i topi KO infatti presentavano un maggior numero di granulociti ma un ridotto numero di linfociti circolanti. Questi risultati suggeriscono che i BM-A possano contribuire alla sopravvivenza delle cellule staminali emopoietiche e che l’APN partecipi alla regolazione dell’emopoiesi normale in condizioni di CR.The bone marrow (BM) niche is a highly specialised microenvironment that provides structural and trophic support through its stromal components for Haematopoietic Stem Cells (HSC). Adipocytes (BM-A) are the most abundant stromal components in the niche, however, their role in haematopoiesis regulation remain unclear. It has been demonstrated that during caloric restriction (CR) there is an expansion of bone marrow adipose tissue and this contributes to increased circulating levels of adiponectin (APN), a hormone potentially involved in haematopoiesis regulation. The aims of our work were to molecularly and functionally characterise BM-A, and to determine if APN contributes to the regulation of the HSC during CR. To address these aims, human BM-A were isolated from hip surgery patients and studied through microarray analysis; while their relationship with HSC was assessed in vitro using long-term co-culture assay with HSC. The role of APN was studied using a mouse model of APN-/- and evaluating the characteristics of HSC and of circulating haematopoietic cells by flow cytometry and by Colony Forming Unit (CFU) assays in mice under CR. Molecular data suggested that BM-A displayed a specific gene expression profile and that they are capable of supporting HSC survival in vitro. Adiponectin KO mouse models showed that KO animals had a reduced number of white blood cells which turned into an increased proportion of Granulocytes in the whole CD45 population and to a significantly reduced number of B cells especially after the first week of CR. These results suggested that BM-A may contribute to the survival of HSC and that APN contributes to the regulation of immune cells during CR

Bone Marrow "Yellow" and "Red" Adipocytes: Good or Bad Cells?

Purpose of Review Replacement of red hematopoietic bone marrow with yellow adipocyte-rich marrow constitutes a physiological process associated with aging. Adipocytes have recently emerged as an active part of the bone marrow niche and exert paracrine and endocrine functions, thereby contributing to the regulation of hematopoiesis. Here, we review the current understanding of the interactions between bone marrow adipocytes (BMAs) and hematopoietic cells, as well as their potential role in the progression of hematological malignancies. Recent Findings Until recently, BMAs have been considered space-filler cells. Emerging evidence, however, associates BMA abundance with hematopoietic regulation. On the one hand, human clinical data and experimental findings from animal models suggest that BMAs may act as negative regulators of the hematopoietic microenvironment. On the other hand, recent data has also shown BMAs to exert positive effects on hematopoietic stem cell (HSC) survival. These seemingly contradictory effects could be explained either by a differential effect of distinctBMAsubtypes on hematopoiesis, or by a differential response to BMAstimulation in HSCs versus their committed progeny. Two distinct types of bone marrow adipocytes have previously been described based on anatomical localization. Adipocytes located in the Byellow^ marrow are bigger in size, less responsive to environmental stimuli, and associated with HSC quiescence. On the contrary, adipocytes situated within regions of hematopoietically active Bred^ marrow are significantly more labile and provide important support to regenerating blood populations. Moreover, beyond the presumed differential role of BMA subtypes in hematopoiesis, an imbalanced proportion of stromal constituents could impair their capacity to provide a protective role. Indeed, if BMA commitment has been shown essential for hematopoietic regeneration, skeletal regions constitutively enriched in BMAwould be poorly vascularized, which would in turn negatively affect HSC support. Recently, the interplay of adipocytes and solid cancer has been revealed, with adipocytes promoting the growth of breast, ovarian and prostate cancers. BMAs have been no exception, playing an active role in the support of neoplastic cells in the bone marrow niche, particularly for bone metastatic disease and acute lymphoblastic leukemia (ALL). Acute myeloid leukemia (AML), however, actively suppresses BMAs, which results in impaired myelo-erythroid maturation. Summary It is becoming increasingly evident that BMAs are ideally placed to interact with normal and malignant hematopoiesis. As such, elucidating the relationship between BMAs and specific hematopoietic cell types represents a novel avenue to explore therapeutic strategies for the treatment of hematological malignancies

Intestinal anisakiasis in Italy: a case treated by emergency surgery

Anisakiasis is a fish-borne zoonotic disease. A case of intestinal anisakiasis in a woman who had consumed raw marinated anchovies was reported. The intestinal localization resulted in occlusive acute abdomen which required an emergency surgical treatment. The histological examination of the eosinophilic granuloma removed from the resected colon revealed the presence of larval nematodes of the genus Anisakis as causative agents

Dynamics of short pulses and phase matched second harmonic generation in negative index materials

We study pulsed second harmonic generation in metamaterials under conditions of significant absorption. Tuning the pump in the negative index range, a second harmonic signal is generated in the positive index region, such that the respective indices of refraction have the same magnitudes but opposite signs. This insures that a forward-propagating pump is exactly phase matched to the backward-propagating second harmonic signal. Using peak intensities of ~500 MW/cm2, assuming χ(2)~80pm/V, we predict conversion efficiencies of 12% and 0.2% for attenuation lengths of 50 and 5μm, respectively

Gap solitons in a nonlinear quadratic negative-index cavity

We predict the existence of gap solitons in a nonlinear, quadratic Fabry-Pérot negative index cavity. A peculiarity of a single negative index layer is that if magnetic and electric plasma frequencies are different it forms a photonic band structure similar to that of a multilayer stack composed of ordinary, positive index materials. This similarity also results in comparable field localization and enhancement properties that under appropriate conditions may be used to either dynamically shift the band edge, or for efficient energy conversion. We thus report that an intense, fundamental pump pulse is able to shift the band edge of a negative index cavity, and make it possible for a weak second harmonic pulse initially tuned inside the gap to be transmitted, giving rise to a gap soliton. The process is due to cascading, a well-known phenomenon that occurs far from phase matching conditions that limits energy conversion rates, it resembles a nonlinear third-order process, and causes pulse compression due to self-phase modulation. The symmetry of the equations of motion under the action of either an electric or a magnetic nonlinearity suggests that both nonlinear polarization and magnetization, or a combination of both, can lead to solitonlike pulses. More specifically, the antisymmetric localization properties of the electric and magnetic fields cause a nonlinear polarization to generate a dark soliton, while a nonlinear magnetization spawns a bright soliton. © 2007 The American Physical Society