Neutron and Gamma-Ray Detection System Coupled to a Multirotor for Screening of Shipping Container Cargo.

In order to detect special nuclear materials and other radioactive materials in Security and Defense scenarios, normally, a combination of neutron and gamma-ray detection systems is used. In particular, to avoid illicit traffic of special nuclear materials and radioactive sources/materials, radiation portal monitors are placed at seaports to inspect shipping-container cargo. Despite their large volume (high efficiency), these detection systems are expensive, and therefore only a fraction of these containers are inspected. In this work, a novel mobile radiation detection system is presented, based on an EJ-200 plastic scintillator for the detection of gamma rays and beta particles, and a neutron detector EJ-426HD plastic scintillator (with 6Li) embedded in a compact and modular moderator. The use of silicon photomultipliers in both detectors presented advantages such as lightweight, compactness, and low power consumption. The developed detection system was integrated in a highly maneuverable multirotor. Monte Carlo simulations were validated by laboratory measurements and field tests were performed using real gamma-ray and neutron sources. The detection and localization within one meter was achieved using a maximum likelihood estimation algorithm for 137Cs sources (4 MBq), as well as the detection of 241Am-beryllium (1.45 GBq) source placed inside the shipping container.

Extraction of Polyphenols and Vitamins Using Biodegradable ATPS Based on Ethyl Lactate.

The growing human population, together with the inefficient use of natural resources, has been dramatically increasing the production of food waste, which poses serious economic, environmental, and social problems. Being so, it is necessary to increase the efficiency of food consumption so as to reduce its waste and to convert the remaining residues into societal benefits. Since this biowaste is rich in polyphenols and vitamins, it could become the feedstock for the production of important value-added compounds for the pharmaceutical (e.g., food supplements) and cosmetic (e.g., creams and shampoos) industries. In this work, partition studies of one polyphenol (epicatechin) and two B-complex vitamins (cyanocobalamin and nicotinic acid) were performed in biodegradable Aqueous Two-Phase Systems (ATPS) based on ethyl lactate and on organic salts (disodium tartrate, tripotassium citrate, and trisodium citrate) at 298.15 K and 0.1 MPa. The largest partition coefficient (K) and extraction efficiency (E) were obtained for vitamin B12 (K=78.56, E=97.5%) for the longest tie line TLL=77.66% in the ATPS {ethyl lactate (1) + tripotassium citrate (2) + water (3)}. All the extractions were obtained with low biomolecule mass losses in quantification (<5%) and after a thorough study of pH influence in the UV−Vis absorbance spectra.

Doxorubicin generates senescent microglia that exhibit altered proteomes, higher levels of cytokine secretion, and a decreased ability to internalize amyloid ß.

Cellular senescence is defined by irreversible cell-cycle arrest and is an evolutionarily conserved hallmark of aging. In this study, we generate senescent microglial cells via exposure to the chemotherapy drug doxorubicin. Compared to control cells, doxorubicin-treated microglia exhibited an altered morphology characterized by an enlarged cell size, a flattened appearance, and the development of prominent filaments. Senescent cells harbored elevated levels of senescence associated-ß-galactosidase, p16Ink4a, and γ-H2AX. Senescent microglia were also less efficient at internalizing amyloid ß and pHrodo bioparticles. A detailed proteomic analysis using SWATH-MS identified 201 proteins that were significantly downregulated and 127 that were significantly upregulated in doxorubicin-treated microglia. Proteins involved in processes such as protein synthesis, RNA damage and repair, and protein degradation were largely downregulated while those compromising the integrity of the cell were predominantly upregulated. Various proteins involved in proteasomal processing were among the most significantly downregulated in senescent cells. Relevant to the deleterious senescence-associated secretory phenotype, senescent cells secreted higher levels of the inflammatory cytokines IL-6, IL-8, TNF-α, and GRO-α. Our data suggest that symptoms of brain aging and age-related neurodegenerative disease may be partially caused by defective phagocytosis, impaired proteasomal processing, and elevated cytokine secretion of senescent microglia.

State-of-the-Art Mobile Radiation Detection Systems for Different Scenarios.

In the last decade, the development of more compact and lightweight radiation detection systems led to their application in handheld and small unmanned systems, particularly air-based platforms. Examples of improvements are: the use of silicon photomultiplier-based scintillators, new scintillating crystals, compact dual-mode detectors (gamma/neutron), data fusion, mobile sensor networks, cooperative detection and search. Gamma cameras and dual-particle cameras are increasingly being used for source location. This study reviews and discusses the research advancements in the field of gamma-ray and neutron measurements using mobile radiation detection systems since the Fukushima nuclear accident. Four scenarios are considered: radiological and nuclear accidents and emergencies; illicit traffic of special nuclear materials and radioactive materials; nuclear, accelerator, targets, and irradiation facilities; and naturally occurring radioactive materials monitoring-related activities. The work presented in this paper aims to: compile and review information on the radiation detection systems, contextual sensors and platforms used for each scenario; assess their advantages and limitations, looking prospectively to new research and challenges in the field; and support the decision making of national radioprotection agencies and response teams in respect to adequate detection system for each scenario. For that, an extensive literature review was conducted.

A Fast and Precise Tool for Multi-Layer Planar Coil Self-Inductance Calculation.

An open-source tool that allows for a fast and precise analytical calculation of multi-layer planar coils self-inductance, without any geometry limitation is proposed here. The process of designing and simulating planar coils to achieve reliable results is commonly limited on accuracy and or geometry, or are too time-consuming and expensive, thus a tool to speed up this design process is desired. The model is based on Grover equations, valid for any geometry. The validation of the tool was performed through the comparison with experimental measurements, Finite Element Model (FEM) simulations, and the main analytical methods usually used in literature, with errors registered to be below 2.5%, when compared to standard FEM simulations, and when compared to experimental measurements they are below 10% in the case of the 1-layer coils, and below 5% in the 2-layer coils (without taking into consideration the coil connectors). The proposed model offers a new approach to the calculation of the self-inductance of planar coils of several layers that combines precision, speed, independence of geometry, easy interaction, and no need for extra resources.

e-CoVig: A Novel mHealth System for Remote Monitoring of Symptoms in COVID-19.

In 2019, a new virus, SARS-CoV-2, responsible for the COVID-19 disease, was discovered. Asymptomatic and mildly symptomatic patients were forced to quarantine and closely monitor their symptoms and vital signs, most of the time at home. This paper describes e-CoVig, a novel mHealth application, developed as an alternative to the current monitoring paradigm, where the patients are followed up by direct phone contact. The e-CoVig provides a set of functionalities for remote reporting of symptoms, vital signs, and other clinical information to the health services taking care of these patients. The application is designed to register and transmit the heart rate, blood oxygen saturation (SpO2), body temperature, respiration, and cough. The system features a mobile application, a web/cloud platform, and a low-cost specific device to acquire the temperature and SpO2. The architecture of the system is flexible and can be configured for different operation conditions. Current commercial devices, such as oximeters and thermometers, can also be used and read using the optical character recognition (OCR) functionality of the system. The data acquired at the mobile application are sent automatically to the web/cloud application and made available in real-time to the medical staff, enabling the follow-up of several users simultaneously without the need for time consuming phone call interactions. The system was already tested for its feasibility and a preliminary deployment was performed on a nursing home showing promising results.

Genome-wide association study of agronomic traits in rice cultivated in temperate regions.

BACKGROUND: Rice plants are sensitive to the agro-climate conditions, being photoperiod one of main factor contributing to their adaptation to the region where they are grown. Dissecting the genetic bases underlying diversity in rice populations adapted to specific environmental conditions is a fundamental resource for breeding. In this study we have analysed a collection of japonica varieties adapted to temperate regions to perform association studies with traits of high agronomical interest such as heading date, plant height, number of panicles, panicle length and number of grains per panicle. RESULTS: We have performed a genome wide association study using a panel of 1713 SNPs that, based on previous linkage disequilibrium estimations, provides a full coverage of the whole genome. We have found a total of 43 SNPs associated with variations in the different traits. The identified SNPs were distributed across the genome except in chromosome 12, where no associated SNPs were found. The inspection of the vicinity of these markers also revealed a set of genes associated with physiological functions strongly linked to agronomic traits. Of special relevance are two genes involved in gibberellin homeostasis that are associated with plant height and panicle length. We also detected novel associated sites with heading date, panicle length and number of grain per panicle. CONCLUSION: We have identified loci associated with important agronomic traits among cultivars adapted to temperate conditions. Some of these markers co-localized with already known genes or QTLs, but the association also provided novel molecular markers that can be of help to elucidate the complicated genetic mechanism controlling important agronomic traits, as flowering regulation in the non-dependent photoperiod pathway. The detected associated markers may provide important tools for the genetic improvement of rice cultivars in temperate regions.

Error Recovery in the Time-Triggered Paradigm with FTT-CAN.

Data networks are naturally prone to interferences that can corrupt messages, leading to performance degradation or even to critical failure of the corresponding distributed system. To improve resilience of critical systems, time-triggered networks are frequently used, based on communication schedules defined at design-time. These networks offer prompt error detection, but slow error recovery that can only be compensated with bandwidth overprovisioning. On the contrary, the Flexible Time-Triggered (FTT) paradigm uses online traffic scheduling, which enables a compromise between error detection and recovery that can achieve timely recovery with a fraction of the needed bandwidth. This article presents a new method to recover transmission errors in a time-triggered Controller Area Network (CAN) network, based on the Flexible Time-Triggered paradigm, namely FTT-CAN. The method is based on using a server (traffic shaper) to regulate the retransmission of corrupted or omitted messages. We show how to design the server to simultaneously: (1) meet a predefined reliability goal, when considering worst case error recovery scenarios bounded probabilistically by a Poisson process that models the fault arrival rate; and, (2) limit the direct and indirect interference in the message set, preserving overall system schedulability. Extensive simulations with multiple scenarios, based on practical and randomly generated systems, show a reduction of two orders of magnitude in the average bandwidth taken by the proposed error recovery mechanism, when compared with traditional approaches available in the literature based on adding extra pre-defined transmission slots.

Ultrafast Generation of Unconventional {001} Loops in Si.

Ultrafast laser annealing of ion implanted Si has led to thermodynamically unexpected large {001} self-interstitial loops, and the failure of Ostwald ripening models for describing self-interstitial cluster growth. We have carried out molecular dynamics simulations in combination with focused experiments in order to demonstrate that at temperatures close to the melting point, self-interstitial rich Si is driven into dense liquidlike droplets that are highly mobile within the solid crystalline Si matrix. These liquid droplets grow by a coalescence mechanism and eventually transform into {001} loops through a liquid-to-solid phase transition in the nanosecond time scale.

Correction of a Cystic Fibrosis Splicing Mutation by Antisense Oligonucleotides.

Cystic fibrosis (CF), the most common life-threatening genetic disease in Caucasians, is caused by ∼2,000 different mutations in the CF transmembrane conductance regulator (CFTR) gene. A significant fraction of these (∼13%) affect pre-mRNA splicing for which novel therapies have been somewhat neglected. We have previously described the effect of the CFTR splicing mutation c.2657+5G>A in IVS16, showing that it originates transcripts lacking exon 16 as well as wild-type transcripts. Here, we tested an RNA-based antisense oligonucleotide (AON) strategy to correct the aberrant splicing caused by this mutation. Two AONs (AON1/2) complementary to the pre-mRNA IVS16 mutant region were designed and their effect on splicing was assessed at the RNA and protein levels, on intracellular protein localization and function. To this end, we used the 2657+5G>A mutant CFTR minigene stably expressed in HEK293 Flp-In cells that express a single copy of the transgene. RNA data from AON1-treated mutant cells show that exon 16 inclusion was almost completely restored (to 95%), also resulting in increased levels of correctly localized CFTR protein at the plasma membrane (PM) and with increased function. A novel two-color CFTR splicing reporter minigene developed here allowed the quantitative monitoring of splicing by automated microscopy localization of CFTR at the PM. The AON strategy is thus a promising therapeutic approach for the specific correction of alternative splicing.

Dynamics of Akt activation during mouse embryo development: distinct subcellular patterns distinguish proliferating versus differentiating cells.

Akt is a highly conserved serine-threonine protein kinase which has been implicated in a wide variety of cellular functions, from the regulation of growth and metabolism, to activation of pro-survival pathways and cell proliferation, and promotion of differentiation in specific cell types. However, very little is known about the spatial and temporal pattern of Akt activity within cells and whether this pattern changes as cells enter and proceed in their differentiation programs. To address this issue we profiled Akt activation in E8.5-E13.5 mouse embryos and in C2C12 cells. We used a commercial antibody against Akt, phosphorylated on one of its activating residues, Thr-308, and performed high resolution confocal imaging of the immunofluorescence in labeled embryos. We observe strong Akt activity during mitosis in the dermomyotome, the neuroepithelium and some mesenchymal cells. This burst of activity fills the whole cell except for heterochromatin-positive areas in the nucleus. A surge in activity during mitosis is also observed in subconfluent C2C12 cells. Later on in the differentiation programs of skeletal muscle and neural cells, derivatives of the dermomyotome and neuroepithelium, respectively, we find robust, sustained Akt activity in the cytoplasm, but not in the nucleus. Concomitantly with skeletal muscle differentiation, Akt activity becomes concentrated in the sarcomeric Z-disks whereas developing neurons maintain a uniform cytoplasmic pattern of activated Akt. Our findings reveal unprecedented cellular and subcellular details of Akt activity during mouse embryo development, which is spatially and temporally consistent with proposed functions for Akt in mitosis and myogenic and neural differentiation and/or survival. Our results thus demonstrate a subcellular change in the pattern of Akt activation when skeletal muscle and neural progenitor cells cease dividing and progress in their differentiation programs.

Possible adverse reactions to herbal products: a study with individuals who resort to popular medicine in the city of Diadema, SP, Brazil.

The present study aimed to investigate the occurrence of adverse reactions (ADRs) related to herbal products (HPs), which are purchased over-the-counter for self-treatment, reported by 100 users. Samples of the HPs related to those ADRs were purchased for their pharmacobotanical identification. The ADRs reported were evaluated based on specialized literature and were analyzed according to causality into probable (PR), possible (PO), unrelated (UR) or unclassifiable (UC); according to expectance into unexpected adverse reaction (UNEX) and expected adverse reaction (EX); seriousness into serious adverse event or reaction (S) and non-serious (NS); and severity into mild (MI), moderate (MO) and severe (SE). Among 100 interviews, five complaints of ADRs were reported in relation to HPs: Senna alexandrina, with a report of cramps (PR; MI; EX; NS); Camellia sinensis, associated with tachycardia (PO; MI; EX; NS); Bauhinia sp., a strong allergic reaction that led to hospitalization (UC; MO; UNEX; S); Picrasma crenata, with several symptoms and hospitalization (UR; MO; UNEX; S); and 21-herb tea, related to an allergic reaction (UC; MI; EX; NS). The strategies used in this study allowed us to carry out an analysis of ADRs attributed to HPs. This analysis could serve as a model in the study of similar cases.

Epidemiology of horse pythiosis in the Pantanal of Mato Grosso: Exploring the host-parasite-vector relationship.

Horse pythiosis is considered an endemic disease in the Brazilian Pantanal region, causing devastating health and economic losses. This study aimed to enhance the understanding of pythiosis epidemiology, map the distribution of horse body lesions, and investigate the correlation between these lesions and warm body surface areas, potentially implicating hematophagous vectors in the disease's transmission. A prospective study was conducted on equids in the Pantanal Mato-grossense and adjacent areas from 2012 to 2022, with 112 horses and three mules diagnosed with pythiosis. Clinical and epidemiological data, lesions' photographic records, and healthy equids' thermal imaging were collected. Most pythiosis cases occurred between January and March, correlating with regional flood cycles. Most lesions were found on limbs and the ventral abdomen, with dark-colored horses exhibiting a higher frequency of lesions. Interestingly, the thermal mapping revealed that warm areas on a healthy horse's body overlapped significantly with lesion distribution - blood-sucking insects also prefer these areas. The results suggest that pythiosis lesions in horses correlate with warmer areas of the animal body, reinforcing the hypothesis of vector involvement in disease transmission. This study underscores the need for further observational research to fully understand the complex epidemiological dynamics of pythiosis in horses.

Robust multiferroicity and magnetic modulation of the ferroelectric imprint field in heterostructures comprising epitaxial Hf0.5Zr0.5O2 and Co.

Magnetoelectric multiferroics, either single-phase or composites comprising ferroelectric/ferromagnetic coupled films, are promising candidates for energy efficient memory computing. However, most of the multiferroic magnetoelectric systems studied so far are based on materials that are not compatible with industrial processes. Doped hafnia is emerging as one of the few CMOS-compatible ferroelectric materials. Thus, it is highly relevant to study the integration of ferroelectric hafnia into multiferroic systems. In particular, ferroelectricity in hafnia, and the eventual magnetoelectric coupling when ferromagnetic layers are grown atop of it, are very much dependent on quality of interfaces. Since magnetic metals frequently exhibit noticeable reactivity when grown onto oxides, it is expected that ferroelectricity and magnetoelectricity might be reduced in multiferroic hafnia-based structures. In this article, we present excellent ferroelectric endurance and retention in epitaxial Hf0.5Zr0.5O2 films grown on buffered silicon using Co as the top electrode. The crucial influence of a thin Pt capping layer grown on top of Co on the ferroelectric functional characteristics is revealed by contrasting the utilization of Pt-capped Co, non-capped Co and Pt. Magnetic control of the imprint electric field (up to 40% modulation) is achieved in Pt-capped Co/Hf0.5Zr0.5O2 structures, although this does not lead to appreciable tuning of the ferroelectric polarization, as a result of its high stability. Computation of piezoelectric and flexoelectric strain-mediated mechanisms of the observed magnetoelectric coupling reveal that flexoelectric contributions are likely to be at the origin of the large imprint electric field variation.

Growth of emergent simple pseudo-binary ferroelectrics and their potential in neuromorphic computing devices.

Ferroelectric memory devices such as ferroelectric memristors, ferroelectric tunnel junctions, and field-effect transistors are considered among the most promising candidates for neuromorphic computing devices. The promise arises from their defect-independent switching mechanism, low energy consumption and high power efficiency, and important properties being aimed for are reliable switching at high speed, excellent endurance, retention, and compatibility with complementary metal-oxide-semiconductor (CMOS) technology. Binary or doped binary materials have emerged over conventional complex-composition ferroelectrics as an optimum solution, particularly in terms of CMOS compatibility. The current state-of-the-art route to achieving superlative ferroelectric performance of binary oxides is to induce ferroelectricity at the nanoscale, e.g., in ultra-thin films of doped HfO2, ZrO2, Zn1-xMgxO, Al-xScxN, and Bi1-xSmxO3. This short review article focuses on the materials science of emerging new ferroelectric materials, including their different properties such as remanent polarization, coercive field, endurance, etc. The potential of these materials is discussed for neuromorphic applications.

High-performance and self-powered visible light photodetector using multiple coupled synergetic effects.

In this work, we demonstrate, for the first time, that coupling together the pyroelectric effect, the photovoltaic effect and the plasmonic effect is a novel method to significantly enhance the performance of self-powered photodetectors in the visible region. Photodetectors based on tri-layered heterojunction of n-Si/p-SnO/n-ZnO through the inclusion of silver (Ag) nanoparticles (NPs) at the SnO/ZnO interface were fabricated. The photo-response of the device, with excitation from a chopped 650 nm wavelength laser, was carefully investigated, and it was shown that the photodetector performance is enhanced the most with the inclusion of spheroidal Ag NPs with ∼70 nm diameter. The Al/Si/SnO/Ag NPs/ZnO/ITO device exhibited an optimum responsivity, detectivity and sensitivity of 210.2 mA W-1, 5.47 × 109 Jones and 15.0 × 104, respectively, together with a rise and fall time of 2.3 and 51.3 µs, respectively, at a laser power density of 317 mW cm-2 and at a chopper frequency of 10 Hz. The present photodetectors are more than twice as responsive as the current best-performing ZnO-based pyro-phototronic photodetectors and they also exhibit other competitive features, such as detectivity, and fall and rise times. Therefore, by exploiting the plasmonic effect of the Ag NPs together with the pyroelectric effect in a ZnO film, and the photovoltaic effect at a Si/SnO junction, all in a single device, photodetectors were developed with state-of-the-art performance for the visible region.

Exploiting Leishmania-Primed Dendritic Cells as Potential Immunomodulators of Canine Immune Response.

Dendritic cells (DCs) capture pathogens and process antigens, playing a crucial role in activating naïve T cells, bridging the gap between innate and acquired immunity. However, little is known about DC activation when facing Leishmania parasites. Thus, this study investigates in vitro activity of canine peripheral blood-derived DCs (moDCs) exposed to L. infantum and L. amazonensis parasites and their extracellular vesicles (EVs). L. infantum increased toll-like receptor 4 gene expression in synergy with nuclear factor κB activation and the generation of pro-inflammatory cytokines. This parasite also induced the expression of class II molecules of major histocompatibility complex (MHC) and upregulated co-stimulatory molecule CD86, which, together with the release of chemokine CXCL16, can attract and help in T lymphocyte activation. In contrast, L. amazonensis induced moDCs to generate a mix of pro- and anti-inflammatory cytokines, indicating that this parasite can establish a different immune relationship with DCs. EVs promoted moDCs to express class I MHC associated with the upregulation of co-stimulatory molecules and the release of CXCL16, suggesting that EVs can modulate moDCs to attract cytotoxic CD8+ T cells. Thus, these parasites and their EVs can shape DC activation. A detailed understanding of DC activation may open new avenues for the development of advanced leishmaniasis control strategies.

A Pax3/Dmrt2/Myf5 regulatory cascade functions at the onset of myogenesis.

All skeletal muscle progenitor cells in the body derive from the dermomyotome, the dorsal epithelial domain of developing somites. These multipotent stem cells express Pax3, and this expression is maintained in the myogenic lineage where Pax3 plays an important role. Identification of Pax3 targets is therefore important for understanding the mechanisms that underlie the onset of myogenesis. In a microarray screen of Pax3-GFP sorted cells, with analysis on Pax3 gain and loss of function genetic backgrounds, we identify Dmrt2, expressed in the dermomyotome, as a Pax3 target. In vitro gel shift analysis and chromatin immunoprecipitation with in vivo extracts show that Pax3 binds to a conserved 286 bp sequence, situated at -18 kb from Dmrt2. This sequence directs reporter transgene expression to the somite, and this is severely affected when the Pax3 site is mutated in the context of the locus. In Dmrt2 mutant embryos, somite maturation is perturbed and the skeletal muscle of the myotome is abnormal. We now report that the onset of myogenesis is also affected. This depends on activation, in the epaxial dermomyotome, of the myogenic determination gene, Myf5, through its early epaxial enhancer. This sequence contains sites that bind Dmrt2, which belongs to the DM class of DNA-binding proteins. Mutation of these sites compromises activity of the enhancer in transgenic embryos where the reporter transgene is under the control of the Myf5 epaxial enhancer. Transactivation of this site by Dmrt2 is demonstrated in vitro, and conditional overexpression of Dmrt2 in Pax3 expressing cells in the somite confirms the role of this factor in the activation of Myf5. These results reveal a novel genetic network, comprising a Pax3/Dmrt2/Myf5 regulatory cascade that operates in stem cells of the epaxial dermomyotome to initiate skeletal muscle formation.

Molecular Dynamics Simulation of Ti Metal Cutting Using a TiN:Ag Self-Lubricating Coated Tool.

Silver-ceramic nanocomposite coatings, such as TiN:Ag, are among the most interesting solutions to improve the machining and cutting process of hard-to-cut Ti alloys, since they combine the TiN matrix hardness with the lubricating and protective action of Ag nanoparticles. Therefore, it is important to understand how, when present, Ag distributes at the tool-workpiece interface and how it affects the tribolayer formation and the tool wear. Molecular dynamics simulation results, obtained using a MEAM-based force field, are presented here for the cutting process of a Ti workpiece with a TiN tool, with and without the presence of Ag at the interface, for different cutting speeds. Ag is shown to form a thin protective layer at the workpiece-tool interface that prevents a direct contact between the parts and greatly reduces the tool degradation. Our simulations confirm the importance of Ag in self-lubricating nanocomposite coatings to realize the machining of otherwise hard-to-cut materials.

Oxygen Adsorption on Polar and Non-Polar Zn:ZnO Heterostructures from First Principles.

Zn:ZnO nanostructures have been studied extensively due to their potential use in many applications, such as oxygen scavengers for food packaging applications. Under atmospheric conditions, ZnO grows on the surface of Zn via an oxidation process. The mechanisms governing Zn oxidation are still not fully understood, with classical oxidation models, such as the Cabrera Mott, underestimating the oxide thickness of Zn:ZnO core-shell structures. In this work, Ab initio DFT calculations were performed to assess the adsorption properties of oxygen molecules on Zn:ZnO heterostructures to help elucidate the mechanisms involved in the growth of a ZnO film on a Zn substrate. Results suggest that the charge transfer mechanism from the Zn:ZnO heterostructures to the adsorbed oxygen layer can be promoted by two different processes: the electronic doping of ZnO due to the formation of the Zn:ZnO interface and the excess surface charge due to the presence of dangling bonds on the as cleaved ZnO.