Implementação de desmonte com explosivos em Timor-Leste: proposta exploratória

O principal objetivo deste trabalho foi analisar a variação do custo do desmonte com recurso a explosivos em função da escavabilidade do maciço rochoso. Para tal, foram acompanhadas e monitorizados quatro pegas de fogo P1, P3 e P4, da Pedreira de Serdedelo e P2, da Pedreira Fornelo. Antes da implementação do diagrama de fogo e respetiva execução das operações do desmonte, foram previamente bem definidos os locais de cada pega, e, individualmente, realizada uma caracterização do maciço rochoso a desmontar, através de um rigoroso levantamento de cada bancada, recorrendo á técnica de amostragem linear e esclerómetro portátil. Seguidamente, das quatro pegas de fogo, foram registados todos os parâmetros do desmonte e quantificados todos os custos associados aos trabalhos desenvolvidos para as mesmas, desde o levantamento das descontinuidades para caracterização do maciço rochoso a desmontar, até à fragmentação secundária com recurso a meios mecânicos para redução dos calibres resultantes do desmonte que ficaram acima do recomendado para a alimentação do primário. Com base no ábaco Pettifer & Fookes (1994), foi classificada, quanto à sua escavabilidade, o maciço presente em cada bancada a desmontar. Foi criada uma grelha em cima do abaco Pettifer & Fookes (1994), para a respetiva projeção de cada pega no mesmo, com indicação do seu custo unitário de desmonte. Foi realizado este mesmo exercício para uma pega em Timor-Leste, onde são utilizados apenas meios mecânicos para o desmonte, e foi projetado um desmonte teórico com recurso a explosivos, para comparação dos custos do desmonte de diferentes técnicas. A pega P3 apresenta a menor escavabilidade e consequentemente o custo mais elevado (2,463 €/m3 ), em oposição a P2 apresenta a melhor escavabilidade e o menor custo (1,854 €/m3 ). O desmonte mecânico em Timor-Leste tem, atualmente, um custo de 3,39 €/m3 , enquanto a projeção teórica de uma pega com recurso a explosivos tem um custo estimado de 1,450 €/m3 . Podemos concluir que existe uma assinalável relação entre a escavabilidade do maciço rochoso e o respetivo custo do desmonte. Na pega de Timor-Leste, fica clara a grande mais valia económica do desmonte a fogo, quando comparado com o desmonte com meios mecânicos para maciços neste espectro de escavabilidade.The main objective of this study is to analyze the variation of the rock cost blasting cost using explosives according to the excavatability of the rock mass. To achieve this, four blasting projects were carried out and monitored. Blasting P1, P3 and P4 are from the Serdedelo Quarry, while blasting P2 is from the Fornelo Quarry. The locations of each blasting were defined before applying and executing the project design of blasting operations. The rock mass to be excavated was individually characterized by rigorous data collectors of each bench using the scanline sample techniques and Schmidt hammer. All the parameters of the blasting were recorded, and quantified all the costs associated with the four blasting operations, covered from field surveying of the bench, characterizing the rock mass to be excavated up to the secondary fragmentation, using hydraulic breaking to reduce the large rock blocks that exceeded the recommended primary feed. Based on the abacus Pettifer & Fookes (1994), each bench to be excavated was classified as to its excavatability whereby a grid was created over abacus for each of the aforementioned rock blasting operations and indicating their unit costs. The same assignment was carried out for a blasting in Timor-Leste, where only mechanical excavations are used for breaking the rocks, and a theoretical blasting with explosives was designed to compare the costs of different techniques of excavation. Blasting P3 has the lowest excavatability and therefore showed the highest cost of (2.463 €/m3 ), while blasting P2 has the best excavatability and with the lowest cost of (1.854 €/m3 ). The mechanical excavation in TimorLeste has a cost of 3.39 €/m3 , while the theoretical blasting has estimated cost of 1.45 €/m3 . We can conclude therefore, that there is a remarkable relationship between the rock mass excavatability and the respective cost of the blasting. Timor-Leste's blasting clearly proved the great economic value compared to mechanical excavation for the rock masses of this range of excavatability

An integrative literature review on the SARS-CoV-2 virus from 2015 to 2022

Coronaviruses of the order Nidovirales and families Coronaviridae, Arteriviridae, Mesoniviridae, Roniviridae were first isolated in 1937 and described in 1965. In 2019, the SARS-CoV-2 coronavirus was responsible for the coronavirus disease in 2019 (COVID-19) in Worldwide. Due to the great importance of SARS-CoV-2, this study integrated information about the virus, as a response: its origin, diagnosis and treatment, diagnosis and treatment. For this, a bibliographic survey was carried out in the Scielo, PubMed and Google Scholar databases regarding SARS-CoV-2, in order to describe its characteristics. SARS-CoV-2 does not yet have a well-clarified pathophysiology, it is known that it can cause an acute or chronic lung injury and that this condition resembles SARS-CoV, which results in aggressive inflammation initiated by viral replication. Both SARS-CoV and SARS-CoV-2 replicated similarly in alveolar epithelium, but SARS-CoV-2 replicates extensively in bronchial epithelium. Reverse transcription followed by polymerase chain reaction (RT-PCR) is widely used to identify viruses that cause respiratory secretions. Currently, with an ongoing viral pandemic, the importance of identifying the pathophysiological characteristics of SARS-CoV-2 and its serious impact on global public health becomes increasingly evident, especially with regard to the remarkable overload of health services, both private and public

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Combined fit to the spectrum and composition data measured by the Pierre Auger Observatory including magnetic horizon effects

The measurements by the Pierre Auger Observatory of the energy spectrum and mass composition of cosmic rays can be interpreted assuming the presence of two extragalactic source populations, one dominating the flux at energies above a few EeV and the other below. To fit the data ignoring magnetic field effects, the high-energy population needs to accelerate a mixture of nuclei with very hard spectra, at odds with the approximate E$^{-2}$ shape expected from diffusive shock acceleration. The presence of turbulent extragalactic magnetic fields in the region between the closest sources and the Earth can significantly modify the observed CR spectrum with respect to that emitted by the sources, reducing the flux of low-rigidity particles that reach the Earth. We here take into account this magnetic horizon effect in the combined fit of the spectrum and shower depth distributions, exploring the possibility that a spectrum for the high-energy population sources with a shape closer to E$^{-2}$ be able to explain the observations

Studies of the mass composition of cosmic rays and proton-proton interaction cross-sections at ultra-high energies with the Pierre Auger Observatory

In this work, we present an estimate of the cosmic-ray mass composition from the distributions of the depth of the shower maximum (Xmax) measured by the fluorescence detector of the Pierre Auger Observatory. We discuss the sensitivity of the mass composition measurements to the uncertainties in the properties of the hadronic interactions, particularly in the predictions of the particle interaction cross-sections. For this purpose, we adjust the fractions of cosmic-ray mass groups to fit the data with Xmax distributions from air shower simulations. We modify the proton-proton cross-sections at ultra-high energies, and the corresponding air shower simulations with rescaled nucleus-air cross-sections are obtained via Glauber theory. We compare the energy-dependent composition of ultra-high-energy cosmic rays obtained for the different extrapolations of the proton-proton cross-sections from low-energy accelerator data

Study of downward Terrestrial Gamma-ray Flashes with the surface detector of the Pierre Auger Observatory

The surface detector (SD) of the Pierre Auger Observatory, consisting of 1660 water-Cherenkov detectors (WCDs), covers 3000 km2 in the Argentinian pampa. Thanks to the high efficiency of WCDs in detecting gamma rays, it represents a unique instrument for studying downward Terrestrial Gamma-ray Flashes (TGFs) over a large area. Peculiar events, likely related to downward TGFs, were detected at the Auger Observatory. Their experimental signature and time evolution are very different from those of a shower produced by an ultrahigh-energy cosmic ray. They happen in coincidence with low thunderclouds and lightning, and their large deposited energy at the ground is compatible with that of a standard downward TGF with the source a few kilometers above the ground. A new trigger algorithm to increase the TGF-like event statistics was installed in the whole array. The study of the performance of the new trigger system during the lightning season is ongoing and will provide a handle to develop improved algorithms to implement in the Auger upgraded electronic boards. The available data sample, even if small, can give important clues about the TGF production models, in particular, the shape of WCD signals. Moreover, the SD allows us to observe more than one point in the TGF beam, providing information on the emission angle

The dynamic range of the upgraded surface-detector stations of AugerPrime

The detection of ultra-high-energy cosmic rays by means of giant detector arrays is often limited by the saturation of the recorded signals near the impact point of the shower core at the ground, where the particle density dramatically increases. The saturation affects in particular the highest energy events, worsening the systematic uncertainties in the reconstruction of the shower characteristics. The upgrade of the Pierre Auger Observatory, called AugerPrime, includes the installation of an 1-inch Small PhotoMultiplier Tube (SPMT) inside each water-Cherenkov station (WCD) of the surface detector array. The SPMT allows an unambiguous measurement of signals down to about 250m from the shower core, thus reducing the number of events featuring a saturated station to a negligible level. In addition, a 3.8m2 plastic scintillator (Scintillator Surface Detector, SSD) is installed on top of each WCD. The SSD is designed to match the WCD (with SPMT) dynamic range, providing a complementary measurement of the shower components up to the highest energies. In this work, the design and performances of the upgraded AugerPrime surface-detector stations in the extended dynamic range are described, highlighting the accuracy of the measurements. A first analysis employing the unsaturated signals in the event reconstruction is also presented