bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relación del El Tipo de Cambio Real y las Exportaciones en Nicaragua: una Aplicación de Vectores Autorregresivos (VAR)
Authors: Morales Rivas Oliver David 
Published: June 2017

El presente estudio tiene como objetivo evaluar la relación entre las exportaciones nicaragüense y la evolución del Tipo de Cambio Real (TCR), se aplicó técnicas cuantitativas y de series de tiempo mensual, para el periodo 2006-2016. Los resultados indican que mediante el modelo VAR, se logra comprobar que la variable tipo de cambio real impacta significativamente en las exportaciones de Nicaragua. Sin embargo la magnitud del impacto dependerá en gran medida de la política comercial que adopte Nicaragua para promover un nivel de diversificación de mercado y de productos para exportaciones.
Estimación de la evasión en el Impuesto al Valor Agregado: 2006-2015
Authors: Flores Méndez Leonel Antonio 
Published: June 2017

Este estudio tiene como objetivo estimar la evasión en el IVA en Nicaragua, aplicando el Método Potencial Teórico Usando las Cuentas Nacionales, atendiendo las ventajas que presenta en bajos costos relativos a su implementación y la posibilidad de construir series de evasión, que a su vez permite evaluar la tendencia del incumpliendo y la efectividad de la Administración Tributaria. Más específicamente se eligió utilizar el método del IVA no deducible, debido a que no existen matrices de insumo-productos que permitan llevar a cabo una estimación mediante el método del valor agregado y la carencia de información no permite desarrollar plenamente diferentes metodologías. El estudio revela que el porcentaje de evasión ha venido disminuyendo gradualmente, para el año 2006 significaba el 40.5% y este disminuye diez puntos porcentuales y se sitúa en 30.3% en el año 2015.
Evaluation of Graphene as a Solid-Phase Extraction Sorbent for the Preconcentration and Determination of Trace Amounts of Nickel in Food Samples Prior to Flame Atomic Absorption Spectrometry
Authors: Ebrahimi Bahram , Bahar Soleiman , Moedi Seyde Elham 
Published: June 2017

Abstract
A sensitive and low cost SPE method for the extraction, preconcentration, and flame atomic absorption spectrometric determination of nickel at ng/mL levels is described. Parameters governing the extraction efficiency including pH of the solution, eluent type, sample volume, and matrix ions were investigated for optimization of the presented procedure. The enhancement factor was calculated as 96.5. The calibration curve was linear with R2 of 0.999 in the concentration range from 2 to 200 ng/mL. The RSD was 5.35% (n = 7), the LOD was 0.588 ng/mL, and relative recoveries from vegetable samples ranged between 99 and 109.5%.
Plataformas de descubrimiento en bibliotecas universitarias: evaluación de Worldcat local en el contexto de una biblioteca caribeña
Authors: Montalvo Montalvo Marilyn 
Published: June 2017

Se presenta una evaluación amplia de Worldcat Local (WCL), a la luz de su implementación en el Sistema de Bibliotecas de la Universidad de Puerto Rico en Río Piedras (SB). Primeramente, se realiza una descripción detallada de su estructura, alcance, proceso de configuración e interfaz de búsqueda para explorar cómo sus rasgos inciden en la experiencia de descubrimiento. En segundo lugar, se ofrecen los resultados de un sondeo realizado entre la comunidad universitaria para conocer su opinión sobre el metabuscador. Se concluye que, si bien WCL no ha llenado las expectativas del SB desde la óptica administrativa, los usuarios valoran la disponibilidad de una herramienta que les permita agilizar la búsqueda de información.
SYNTHESIS AND REACTIVITY OF 4-NITRO-3-(TETRAZOL-5-YL) FURAZAN WITH N- AND O-NUCLEOPHILES
Authors: Stepanova Elena V. , Stepanov Andrei I. 
Published: June 2017

A rational four-stages scheme for the synthesis of 4-nitro-3-(tetrazol-5-yl)furazane is proposed. The synthesis starts from the stage of 3-amino-4-(1,2,4-oxadiazol-3-yl)-furazan preparation by condensation of amidoxime of 4-aminofurazan-3-carboxylic acid with triethyl orthoformate, further reductive ring opening of 1,2,4-oxadiazole cycle. The action of hydrazine results in amidrazone of 4-aminofurazan-3-carboxylic acid formation. On the next step the diazotization of the resulting compound with sodium nitrite in acetic acid gives 3-amino-4-(tetrazol-5-yl)furazane. At last stage the titled 4-nitro-3-(tetrazol-5-yl)furazan was synthesized by oxidation of the amino group of 3-amino-4-(tetrazol-5-yl)furazan by a solution of 30% hydrogen peroxide in concentrated sulfuric acid with 85% yield. The increase in the oxidative activity of the H2O2/H2SO4 system by carrying out the oxidation stage at an elevated temperature made possible to substantially reduce the consumption of hydrogen peroxide and sulfuric acid. The desired 4-nitro-3-(tetrazol-5-yl)furazan was isolated by partial neutralization of the reaction mixture with sodium orthophosphate, followed by extraction with ethyl acetate. The total yield of 4-nitro-3-(tetrazol-5-yl)furazane in terms of the starting amidoxime of 4-aminofurazan-3-carboxylic acid was 42-48%. It was shown that the reaction of 4-nitro-3-(tetrazol-5-yl)furazan with a number of N- and O-nucleophilic agents (sodium azide, high-basic amines, hydrazine, sodium hydroxide, methanol in the presence of potassium carbonate) resulted in the substitution of the nitro group of the selected compound by a nucleophile and formation of corresponding 4-R-3-(tetrazol-5-yl)furazane derivatives (R = N3, substituted amino group, NHNH2, OH, OMe). Some chemical properties of thereby obtained compounds are considered. Thus [3 + 2] cycloaddition reaction of 4-azido-3-(tetrazol-5-yl)furazane (R = N3) with propargyl alcohol was used at the synthesis of 4- (4-hydroxy-methyl-1,2,3-triazol-1-yl)-3-(tetrazol-5-yl)furazane. The condensation of 3-hydrazino-4-(tetrazol-5-yl)furazane (R = NHNH2) with carbonyl compounds in the case of reaction with benzaldehyde leads to the corresponding hydrazone, with β-dicarbonyl compounds (malonaldehyde, acetylacetone) pyrazole derivatives were obtained. The synthesized compounds are characterized by 1H and 13C nuclear magnetic resonance spectra, by IR and mass spectroscopy. For citation:Stepanova E.V., Stepanov A.I. Obtaining and Reactivity of 4-nitro-3-(tetrazol-5-yl) furazan with N- and O-nucleophiles. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 5. P. 21-29
Prevalence and outcomes of HIV‐1 diagnostic challenges during universal birth testing – an urban South African observational cohort
Authors: Technau Karl‐Günter , Mazanderani Ahmad Haeri , Kuhn Louise , Hans Lucia , Strehlau Renate , Abrams Elaine J. , Conradie Martie , Coovadia Ashraf , Mbete Ndileka , Murnane Pamela M , Patel Faeezah , Shiau Stephanie , Tiemessen Caroline T. , Sherman Gayle G. 
Published: June 2017

AbstractIntroduction: HIV‐1 polymerase chain reaction (PCR) testing at birth aims to facilitate earlier initiation of antiretroviral therapy (ART) for HIV‐infected neonates. Data from two years of universal birth testing implementation in a high‐burden South African urban setting are presented to demonstrate the prevalence and outcomes of diagnostic challenges in this context.Methods: HIV‐exposed neonates born at Rahima Moosa Mother and Child Hospital between 5 June 2014 and 31 August 2016 were routinely screened at birth for HIV‐1 on whole blood samples using the COBAS® AmpliPrep/COBAS® TaqMan (CAP/CTM) HIV‐1 Qualitative Test, version 2.0 (Roche Molecular Systems, Inc., Branchburg, NJ, USA). Virological results were interpreted according to standard operating procedures with the South African National Health Laboratory Service. All neonates with non‐negative results were actively followed‐up and categorized according to HIV infection status as positive, negative, uncertain and lost to follow‐up (LTFU).Results: 104 (1.8%) of 5743 HIV‐exposed neonates received a non‐negative birth PCR result, for which laboratory data were available for 102 (98%) cases – 78 (76%) tested positive and 24 (24%) indeterminate. HIV infection status was confirmed positive in 83 (81%) infants, negative in 8 (8%), uncertain in 5 (5%) and LTFU in 6 (6%) cases. The positive predictive value (excluding cases of uncertain diagnosis and inadequate testing) following a non‐negative HIV‐1 PCR screening test at birth was 0.91 (83/91; 95% confidence interval: 0.85–0.96). Neonates testing positive at birth had significantly higher viral load (VL) results than those testing indeterminate at birth of 4.5 and 3.0 log copies/ml (p = 0.0007), respectively. Similarly, mothers of neonates with positive as compared to indeterminate birth test results had higher VLs of 4.5 and 2.7 log copies/ml (p = 0.0013), respectively. Half of neonates with an indeterminate birth test were shown to be HIV‐infected on subsequent confirmatory testing, with time to final diagnosis 30 days longer for these neonates (p < 0.0001).Conclusion: Indeterminate HIV‐1 PCR results accounted for a quarter of non‐negative results at birth and were associated with a high risk of infection in comparison to the risk of in utero transmission. Indeterminate birth results with positive HIV PCR results on repeat testing were associated with later final diagnosis. The HIV‐1 status remains uncertain in a minority of cases because of repeatedly indeterminate results, highlighting the need for more sensitive and specific virological tests.
VLF waves from ground‐based transmitters observed by the Van Allen Probes: Statistical model and effects on plasmaspheric electrons
Authors: Ma Qianli , Mourenas Didier , Li Wen , Artemyev Anton , Thorne Richard M. 
Published: June 2017

AbstractWhistler mode very low frequency (VLF) waves from powerful ground‐based transmitters can resonantly scatter energetic plasmaspheric electrons and precipitate them into the atmosphere. A comprehensive 4 year statistics of Van Allen Probes measurements is carried out to assess their consequences on the dynamics of the inner radiation belt and slot region. Statistical models of the measured wave electric field power and of the inferred full wave magnetic amplitude are provided as a function of L, magnetic local time, season, and Kp over L = 1–3, revealing the localization of VLF wave intensity and its variation with geomagnetic activity over 2012–2016. Since this VLF wave model can be directly used together with existing hiss and lightning‐generated wave models in radiation belt simulation codes, we perform numerical calculations of the corresponding quasi‐linear pitch angle diffusion rates, allowing us to demonstrate the crucial role played by VLF waves from transmitters in energetic electron loss at L < 2.5.
Immunity to Infections
Authors: Sehrawat Sharvan , Rouse Barry T 
Published: June 2017

Abstract

Understanding how different pathogens are sensed and recognised by the immune system and an appropriate response generated is critical for devising control strategies. Innate immunity is deployed immediately after the infection, while it takes several days before adaptive immunity effectively kicks in. Key differentiating features of two types of responses are specific recognition and the formation of immunological memory during adaptive immunity. Both types of immune responses are interdependent and play critical role during defence against infections. Recently, emerging trends that challenge well‐established paradigm how innate and adaptive immunity are defined and categorised are highlighted. In addition, factors that make some pathogens less amenable to immune control and unresolved issues in infection immunity are discussed.

Key Concepts

A concerted activity of innate and adaptive immune mechanisms is critical for defence against microbes.

Innate immune responses are not so specific while adaptive immune responses exhibit specificity effected by TCRs and BCRs expressed by T and B cells respectively.

Some mediators however act at the interface of innate and adaptive immunity.

The outcome of infection depends on several host and pathogen properties.

Although most infectious agents utilise strategy to outmanoeuvre immunity but immune evasion is not absolute.

Most chronic infections induce upregulation of inhibitory receptors on T cells a phenomenon commonly known as immune exhaustion.

Blocking signalling induced by inhibitory receptors can reverse function in exhausted T cells.

Immune modulatory strategies could be useful to achieve optimal protection conferred by prophylactic and therapeutic vaccines.
Inflammation: Acute
Authors: Raynes John G 
Published: June 2017

Abstract

Inflammation represents the response of vascularised tissue to damage resulting from infection or injury. An acute inflammatory response comprises four phases: detection of harmful stimuli, response from effector molecules and cells, elimination of pathogens and cellular debris and restoration of tissue homeostasis. Innate pattern recognition molecules are found in extracellular, cell surface and intracellular locations and bind to components of microbes or molecules released by cellular damage. These trigger pathways that lead to the release of inflammatory molecules that alter vascular permeability at sites of tissue damage and activation of many immune cells. Changes in vascular endothelium promote the exudation of plasma and leucocyte recruitment for the clearance of microorganisms and necrotic tissue. Inflammatory mediators also exert systemic effects called the acute‐phase response. Successful clearance of injurious agents and tissue damage abates inflammatory signals and is followed by the formation of granulation tissue and the initiation of tissue remodelling.

Key Concepts

Tissues are continuously surveyed for infection and cellular damage by cells and molecules that recognise pathogen‐ and damage‐associated molecular patterns.

Recognition of infection or cellular damage activates inflammation locally and systemically to activate immune cells and eliminate microbial pathogens and damaged tissue.

Inflammatory signals recruit neutrophils and macrophages into inflamed tissues where they release toxic factors and phagocytose pathogens and cellular debris.

Inflammation has many feedback control mechanisms because if unrestrained it can lead to severe pathology.

The resolution of inflammation is followed by tissue repair and remodelling.
DNA
Methylation and Mutation
Authors: Pfeifer Gerd P 
Published: June 2017

Abstract

Single‐gene and genome sequencing studies have identified base substitution mutations as a causative mechanism in human genetic diseases and cancer. These mutations do not occur randomly but are often enriched at specific DNA (deoxyribonucleic acid) sequences. The genome of most human cells contains about 50 million 5‐methylcytosine bases, the majority of them occurring at the CpG dinucleotide sequence. Methylated CpG dinucleotides are the targets of many of the mutations, mostly transition mutations (C→T or G→A), found in genetic disorders and in malignant tumours. The mechanisms that increase mutations at CpG sites include spontaneous deamination of 5‐methylcytosine and preferential interaction of such sequences with physical or chemical carcinogens. As a consequence of enhanced mutagenesis at methylated CpGs, the CpG frequency in mammalian genomes has been strongly depleted over evolutionary time.

Key Concepts

Methylated CpG sequences are preferentially mutated.

Deamination of 5‐methylcytosine leads to transition mutations at CpGs.

Exogenous carcinogens target methylated CpGs.

CpG mutations are frequent in genetic diseases and cancer.

DNA repair may be affected by methylation of CpG sequences.
HIV
Vaccine Approaches
Authors: Kent Stephen J 
Published: June 2017

Abstract

An HIV (human immunodeficiency virus) vaccine is needed to combat the 1–2 million cases on new HIV infection each year. The goal of vaccination is to establish long‐term immunological readiness that allows rapid protection against infectious disease. All current successful vaccines achieve this by inducing neutralising antibodies, which are effective against acute, cytopathic infections that could otherwise prove fatal. By contrast, potential vaccines against highly variable pathogens that establish persistent infections, such as HIV, have had limited success. There have been multiple attempts to induce effective immunity to HIV in humans, with only one approach showing partial (31%) efficacy. Several clues on a better path forward have, however, emerged from HIV vaccine trials in humans, studies of humans who naturally control HIV infection and studies in animal models. There has been an improved understanding of anti‐HIV neutralising antibodies, which, if could be induced successfully, are likely to be highly effective. Antibodies that engage Fc receptors on innate immune cells (the so‐called ADCC (antibody‐dependent cellular cytotoxicity) antibodies) have emerged as a key component of successful vaccine strategies. New vaccine design and delivery strategies are now entering large‐scale human efficacy trials. These approaches offer real hope that a safe and effective HIV vaccine will eventually be developed to assist in the control of the HIV/AIDS (acquired immunodeficiency syndrome) pandemic.

Key Concepts

A HIV vaccine is urgently needed.

There are many hurdles to induce effective HIV immunity.

Only one HIV vaccine trial in humans has showed partial efficacy to date.

Neutralising antibodies against HIV are highly effective in animal models but are difficult to induce by vaccination.

Functional anti‐HIV antibodies that can engage innate immune cells to fight HIV are likely to be a key component of successful HIV vaccine strategies.

T‐cell‐based immunity against HIV shows promise in certain settings.

New HIV vaccines are entering human efficacy trials.

There is considerable promise that an effective HIV vaccine will be developed in the future.
Immunology of Birds
Authors: Wigley Paul 
Published: June 2017

Abstract

The immune system of birds diverged from that of mammals over 200 million years ago, and although the basic structure and function is largely similar, the immune system of birds is generally more compact and less polymorphic than that of mammals. Birds possess only a single polymorphonuclear leucocyte, the heterophil, but have cellular thrombocytes that may act as phagocytes and antigen‐presenting cells. Recognition of pathogens through pattern recognition is very similar to mammalian species.

Within the adaptive immune response, birds have considerably less polymorphism of major receptor families. The most studied avian species, the chicken, has a compact major histocompatibility complex expressing only two Class I and Class II alleles and evidence of coevolution with major pathogens. There are only three immunoglobulin classes (IgY, IgM and IgA) but three T‐cell receptor classes. Functionally, the system is similar to mammals with cellular (Th1), humoral (Th2), regulatory and Th17 all described in the chicken. Vaccination is a widely used tool in disease control in chickens and other domestic birds. Vaccination technology is particularly advanced and includes the use of drinking water, spray and
in ovo
vaccines to facilitate delivery to large numbers of animals.

Key Concepts

Birds possess a complex immune system which, although shares much of its structure and function with mammals, has differences that reflect 200 million years of divergent evolution.

Most of our knowledge of avian immunology comes from the domestic chicken and the development of vaccines for use by the poultry industry.

B lymphocytes are named after the Bursa of Fabricius, the primary lymphoid organ where they mature in birds.

Birds lack structured peripheral or mesenteric lymph nodes.

The immune system of birds is more compact than that of mammals, with less polymorphism of major receptor families.

Birds have three immunoglobulin or antibody classes compared to five in mammals.

Birds possess three T‐cell receptor types, one more than mammals.

Pattern recognition receptors such as Toll‐like receptors are largely conserved between mammalian and avian species.

Birds possess a single polymorphonuclear cell class, the heterophil, but their nucleated thrombocytes appear to play a key role in innate immunity.

The compact ‘minimal’ major histocompatibility complex of the chicken gives rise to close association between MHC type and resistance to infection.

The need to vaccinate up to 50 billion animals reared each year has driven novel vaccines and delivery systems in the poultry industry.
Brain Growth in

H
omo
erectus
Authors: Cofran Zachary 
Published: June 2017

Abstract

Humans' massive brains stand out as one of our species' defining features. Growth and development are the means by which our large brains are achieved, and these mechanisms also distinguish us from other animals. The evolution of brain growth is difficult to reconstruct as fossil samples are generally small, and brain growth occurs within a minuscule proportion of an individual's life. Although there are several nonadult hominin cranial fossils, the earliest specimen to shed light on this issue is the
Homo erectus
infant from Mojokerto. This infant's proportional brain size is consistent with both human and chimpanzee models of brain growth. On the basis of absolute size, however, this infant implies growth rates that are higher than chimpanzees' and within the modern human range. It is therefore likely that the behaviour and life history of
H. erectus
were more similar to those of modern humans than has generally been appreciated.

Key Concepts

Human brain growth is an important part of our unique life history.

Brain size growth ceases early in life, and so the poor fossil record obfuscates the evolution of brain growth.

Analysis of the Nariokotome adolescent skeleton led to the correct conclusion that human‐like secondary altriciality was present in
Homo erectus
, albeit from the wrong data.

The Mojokerto child's cranium, with an endocranial volume of around 650 cc, is the only
H. erectus
individual that died during the period of brain growth.

The relative brain size of Mojokerto can be found in samples of chimpanzees or humans, meaning proportional brain size does not distinguish patterns of growth.

The finding of a common relationship between neonatal‐adult brain size among catarrhine primates means that a reasonable estimate of neonatal brain size, around 300 cc, can be estimated for
H. erectus
.

Reconstructed brain growth rates, combining the Mojokerto infant's brain size and likely age at death with the species' estimated neonatal brain size, indicate that
H. erectus
was similar to humans in retaining high growth rates for at least a year.
Amado, Jorge
Authors: Norton Wil 
Published: June 2017

Abstract
This entry traces Jorge Amado's aesthetic developments in his novel‐writing. Amado's early novels show an intense focus on socialist realism, and he used the novel form to critique Brazil's treatment of the lower classes. By the 1950s, however, he reinvented his style, recounting more picaresque, humorously ironic portrayals of the ambiguities and inconsistencies in Brazilian society. In tracing Amado's literary history, this entry mentions his involvement in Brazilian leftist politics and his exile in South America and Europe, important events in his development as a novelist.