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The space of light rays N of a conformal Lorentz manifold (M , C) is, under some topological conditions, a manifold whose basic elements are unparametrized null geodesics. This manifold N , strongly inspired on R. Penrose's twistor theory, keeps all information of M and it could be used as a space complementing the spacetime model. In the present review, the geometry and related structures of N , such as the space of skies Σ and the contact structure H , are introduced. The causal structure of M is characterized as part of the geometry of N . A new causal boundary for spacetimes M prompted by R. Low, the L-boundary, is constructed in the case of 3–dimensional manifolds M and proposed as a model of its construction for general dimension. Its definition only depends on the geometry of N and not on the geometry of the spacetime M. The properties satisfied by the L–boundary ∂ M permit to characterize the obtained extension M ¯ = M ∪ ∂ M and this characterization is also proposed for general dimension. [ABSTRACT FROM AUTHOR]

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 or Covid-19), which began as an epidemic in China and spread globally as a pandemic, has necessitated resource management to meet emergency needs of Covid-19 patients and other emergent cases. We have conducted a survey to analyze caseload and measures to adapt indications for a perception of crisis. Methods: We constructed a questionnaire to survey a snapshot of neurosurgical activity, resources, and indications during 1 week with usual activity in December 2019 and 1 week during SARS-CoV-2 pandemic in March 2020. The questionnaire was sent to 34 neurosurgical departments in Europe; 25 departments returned responses within 5 days. Results: We found unexpectedly large differences in resources and indications already before the pandemic. Differences were also large in how much practice and resources changed during the pandemic. Neurosurgical beds and neuro-intensive care beds were significantly decreased from December 2019 to March 2020. The utilization of resources decreased via less demand for care of brain injuries and subarachnoid hemorrhage, postponing surgery and changed surgical indications as a method of rationing resources. Twenty departments (80%) reduced activity extensively, and the same proportion stated that they were no longer able to provide care according to legitimate medical needs. Conclusion: Neurosurgical centers responded swiftly and effectively to a sudden decrease of neurosurgical capacity due to relocation of resources to pandemic care. The pandemic led to rationing of neurosurgical care in 80% of responding centers. We saw a relation between resources before the pandemic and ability to uphold neurosurgical services. The observation of extensive differences of available beds provided an opportunity to show how resources that had been restricted already under normal conditions translated to rationing of care that may not be acceptable to the public of seemingly affluent European countries. [ABSTRACT FROM AUTHOR]

After publication in volume 54, issue 6, 59 the author(s) decided to cancel the Open Access. Correction: The space of light rays: causality and L-boundary "TEXT" https://doi.org/10.1007/s10714-022-02942-3 General Relativity and Gravitation (2022) 54:59. https://doi.org/10.1007/s10714-022-02942-3 The article The space of light rays: Causality and L-boundary, written by A. Bautista, A. Ibort and J. Lafuente, was originally published online on17 June 2022 with Open Access under Creative Commons Attribution (CC BY) licence 4.0. [Extracted from the article]

Rearing in enriched environment (EE) improves the recuperation in animal models of Parkinson’s disease (PD). Administration of TiO2-nanowired cerebrolysin (CBL) could represent an additional strategy to protect or repair the nigrostriatal system. This study aims to explore morphofunctional and biochemical changes in a preclinical stage of PD testing the synergistic efficiency of combining both strategies, housing in EE, and nanodelivery of CBL. Sprague-Dawley male rats receiving intrastriatally 6-hydroxydopamine after a short evolution time were segregated into CBL group (rats receiving nanowired CBL), EE group (rats housed in EE), CBL + EE group (rats housed in EE and receiving nanowired CBL), and control group (rats without additional treatment). Prodromic stage and treatment effects were characterized by the presence of motor symptoms (amphetamine-induced rotational behavior test). Tyrosine hydroxylase (TH) immunohistochemistry and Western blot (p-Akt/Akt and p-ERK/ERK 1/2 as survival markers and caspase-3 as apoptotic marker) were performed in striatum and SN. A decrease in motor symptoms was shown by rats receiving CBL. EE monitoring cages revealed that rats from CBL + EE group showed more significant number of laps in the wheel than EE group. In SN, CBL + EE group also presented the highest neuronal density. Moreover, p-Akt/Akt and p-ERK/ERK 1/2 ratio was significant higher and caspase-3 expression was lower in CBL + EE group. In conclusion, the combination of CBL and EE provided evidence of neuoprotective-neurorestorative mechanisms by which this combined strategy promoted morphofunctional improvement by activation of survival pathways after dopamine depletion in a preclinical model of PD. [ABSTRACT FROM AUTHOR]

Neurotrophic factors (NTFs) are a promising therapeutic option for Parkinson’s disease (PD). They exert their function through tyrosine kinase receptors. Our goal was to assess the effects of administering a selective tyrosine kinase inhibitor (vandetanib) that blocks VEGFR2 and RET receptors in a preclinical model of PD. Rats underwent intrastriatal injections of 6-hydroxydopamine (6-OHDA). Two weeks later, the rats received 30 mg/kg vandetanib or saline orally. The effects were assessed using the rotational behavioral test, tyrosine hydroxylase (TH) immunohistochemistry, and western blot. In 6-OHDA-lesioned rats, motor symptoms were almost undetectable, but morphological and biochemical changes were significant. Vandetanib treatment, combined with the presence of 6-OHDA lesions, significantly increased behavioral impairment and morphological and biochemical changes. Therefore, after vandetanib treatment, the TH-immunopositive striatal volume, the percentage of TH+ neurons, and the extent of the axodendritic network in the substantia nigra decreased. Glial fibrillary acidic protein-positivity significantly decreased in the striatum and substantia nigra in the vandetanib-treated group. In addition, p-Akt and p-ERK 1/2 levels were significantly lower and caspase-3 expression significantly increased after vandetanib administration. In conclusion, we demonstrate for the first time the deleterious effect of a tyrosine kinase inhibitor on the dopaminergic system, supporting the beneficial and synergistic effect of NTFs reported in previous papers. [ABSTRACT FROM AUTHOR]

The unilateral 6-hydroxydopamine (6-OHDA) lesion of medial forebrain bundle (MFB) in rats affords us to study the advanced stages of Parkinson's disease (PD). Numerous evidences suggest synergic effects when various neurotrophic factors are administered in experimental models of PD. The aim of the present work was to assess the morphological changes along the rostro-caudal axis of caudo-putamen complex and substantia nigra (SN) in the referred model in order to test the suitability of a severe model to evaluate new neurorestorative therapies. Administration of 6-OHDA into MFB in addition to a remarkable depletion of dopamine in the nigrostriatal system induced an increase of glial fibrillary acidic protein (GFAP)-positive cells in SN and an intense immunoreactivity for OX-42, vascular endothelial growth factor (VEGF), and Lycopersycum esculentum agglutinin (LEA) in striatum and SN. Tyrosine hydroxylase (TH) immunostaining revealed a significant decrease of the TH-immunopositive striatal volume in 6-OHDA group from rostral to caudal one. The loss of TH-immunoreactive (TH-ir) neurons and axodendritic network (ADN) was higher in caudal sections. Morphological recovery after the implantation of microspheres loaded with VEGF and glial cell line-derived neurotrophic factor (GDNF) in parkinsonized rats was related to the preservation of the TH-ir cell number and ADN in the caudal region of the SN. In addition, these findings support the neurorestorative role of VEGF+GDNF in the dopaminergic system and the synergistic effect between both factors. On the other hand, a topological distribution of the dopaminergic system was noticeable in the severe model, showing a selective vulnerability to 6-OHDA and recovering after treatment. [ABSTRACT FROM AUTHOR]

Finger lesions are a frequent problem because of their functional significance and their small size. Because of this, the radiologist has an important role to play in the correct presurgical diagnosis. The aim of this article is to describe the anatomy and the characteristic US and MR findings of the most common tumor and tumor-like lesions of the fingers, and to discuss the differential diagnosis in cases of unspecific or non-diagnostic findings. We present representative cases selected from 62 patients evaluated at our institution, with pathologic correlation. [ABSTRACT FROM AUTHOR]

Administration of various neurotrophic factors is a promising strategy against Parkinson's disease (PD). An intrastriatal infusion of 6-hydroxidopamine (6-OHDA) in rats is a suitable model to study PD. This work aims to describe stereological parameters regarding rostro-caudal gradient, in order to characterize the model and verify its suitability for elucidating the benefits of therapeutic strategies. Administration of 6-OHDA induced a reduction in tyrosine hidroxylase (TH) reactivity in the dorsolateral part of the striatum, being higher in the caudal section than in the rostral one. Loss of TH-positive neurons and axodendritic network was highly significant in the external third of substantia nigra (e-SN) in the 6-OHDA group versus the saline one. After the administration of nanospheres loaded with neurotrophic factors (NTF: vascular endothelial growth factor (VEGF) + glial cell line-derived neurotrophic factor (GDNF)), parkinsonized rats showed more TH-positive fibers than those of control groups; this recovery taking place chiefly in the rostral sections. Neuronal density and axodendritic network in e-SN was more significant than in the entire SN; the topographical analysis showed that the highest difference between NTF versus control group was attained in the middle section. A high number of bromodeoxyuridine (BrdU)-positive cells were found in sub- and periventricular areas in the group receiving NTF, where most of them co-expressed doublecortin. Measurements on the e-SN achieved more specific and significant results than in the entire SN. This difference in rostro-caudal gradients underpins the usefulness of a topological approach to the assessment of the lesion and therapeutic strategies. Findings confirmed the neurorestorative, neurogenic, and synergistic effects of VEGF + GDNF administration. [ABSTRACT FROM AUTHOR]

The present work discusses the startup and operation of different biotrickling filters during the simultaneous removal of NH, HS, and ethyl mercaptan (EM) for odor control, focusing on (a) the impact of pH control in the stability of the nitrification processes during reactor startup and (b) the crossed effects among selected pollutants and their by-products. Two biotrickling filters were packed with poplar wood chips (R1 and R2A), while a third reactor was packed with polyurethane foam (R2B). R2A and R2B presented a pH control system, whereas R1 did not. Loads of 2-10 g N-NH m h, 5-16 g S-HS m h, and 1-6 g EM m h were supplied to the bioreactors. The presence of a pH control loop in R2A and R2B proved to be crucial to avoid long startup periods and bioreactors malfunctioning due to biological activity inhibition. In addition, the impact of the presence of different concentrations of a series of N species (NH, NO, and NO) and S species (SO and S) on the performance of the two biotrickling filters was studied by increasing their load to the reactors. Sulfide oxidation proved to be the most resilient process, since it was not affected in any of the experiments, while nitrification and EM removal were severely affected. In particular, the latter was affected by SO and NO, while nitrification was significantly affected by NH. The biotrickling filter packed with polyurethane foam was more sensitive to crossed effects than the biotrickling filter packed with poplar wood chips. [ABSTRACT FROM AUTHOR]

This paper analyzes the effects of the introduction of the mini-futures contract in the Spanish stock index futures market. The objective of the paper is twofold: (a) to analyze the potential destabilizing effect of the mini futures trading activity on the distribution of spot returns, and (b) to test whether the mini futures contract significantly contributes to the price discovery process. A non-parametric approach is used to estimate the density function of spot return conditional to both spot and futures trading volume. Empirical findings using 15-min intraday data reveal that the mini futures trading activity enhances the price discovery function of the derivative market and does not destabilize spot prices. [ABSTRACT FROM AUTHOR]

Growth of solid tumors is highly dependent on angiogenesis. During tumor development, neoplastic cells switch to an angiogenic phenotype, playing a significant role in the expression of the vascular endothelial growth factor (VEGF). Seventy-two brain gliomas were induced in Sprague Dawley rats by prenatal exposure to ethylnitrosourea (ENU). Screening and location of tumors was carried out using magnetic resonance imaging (MRI). Conventional histology and immunocytochemistry for antibodies against glial fibrillary acidic protein (GFAP), S-100, NF, oligodendrocyte Ab-2, Ki-67, and VEGF165 were performed. The proliferation index (PI) was calculated from the Ki-67 labeling index, and the concentration of VEGF165 was quantified by enzyme-linked immunosorbent assay (ELISA). In vivo identification of macro- and microtumor appears to be useful to lead morphological and biochemical studies. Histopathology allows us to identify microtumors as classic oligodendrogliomas (CO; mean PI of 6.01 ± 2.8%) and macrotumors as anaplastic oligodendrogliomas (AO; mean PI of 14.06 ± 5%). Classic oligodendrogliomas show scarce VEGF165 expression whereas anaplastic ones display VEGF165 protein level 100-fold increased respect to CO. Astrocytes, neoplastic, and endothelial cells show differential immunostaining patterns from the border to the core of neoplasm. Positive structures for VEGF and their distribution vary according to PI increase. Anaplastic gliomas displaying VEGF-positive intratumor capillaries correspond to the highest PI values. To identify the “angiogenic switch,” we propose the glioma stage characterized by VEGF immunopositive neoplastic cells inside the tumor and positive endothelial cells surrounding it. [ABSTRACT FROM AUTHOR]

Human malignant astrocytic tumors are the most common primary brain malignancies. Human gliomas are classified according to the extent of anaplasia or ‘de-differentiation’ appearance. Although this type of histological classification is widely accepted, the extensive heterogeneity of astrocytic tumors has made their pathological classification rather difficult. New genome-scale high throughput technologies for gene expression profiling, such as DNA microarrays, are emerging as new tools to allow a more accurate identification and characterization of different tumor degrees by discovering new specific markers and pathways of each stage. Present work reports interesting results that might be useful to differentiate between tumor grades. Data presented here provides new evidences about the molecular basis underlying different tumor stages. In this sense, we identified key metabolic pathways, crucial for tumor progression, as being differentially regulated in different tumor stages. On the other hand, remarkable findings regarding Notch pathway are reported, as some members of this receptor family were found to be differentially expressed depending on the malignancy degree. Our results clearly point out important molecular differences between different tumor stages and suggest that more studies are needed to understand specific molecular events characteristic of each stage. These types of studies represent a first step to deepen into the tumor physiology, which may potentially help for better and a more precise diagnosis of gliomas. [ABSTRACT FROM AUTHOR]

VEGF is a major regulator of angiogenesis and vascular permeability in development and injury. The involvement of one of its receptors, Flk-1 in angiogenesis has been widely demonstrated, but few studies elucidate its role as a mediator of the BBB permeability and none displays its distribution following a cortical micronecrosis. A microvascular marker (LEA lectin), two BBB markers (EBA, GluT-1) and the VEGFR2 receptor were studied in adult rats after a minimal brain injury. Immunohistochemistry shows an increase of positive vessels, somata and processes around the micronecrosis from 6 to 72 hours after injury. Flk-1 was overexpressed mainly in endothelial cells, but also in astrocytes, neuronal somata and processes adjacent to the damage. This increase correlates to the lose of positivity for EBA. After injury, VEGFR-2 expression increases and its distribution corresponds to VEGF one. The whole system seems to play a role in the disruption of the BBB. [ABSTRACT FROM AUTHOR]

This work investigates the spatial distribution and species composition of mesopelagic fish larvae and their relationship with the main oceanographic events in the area studied. Samples were collected during a hydrographic and ichthyoplanktonic survey carried out in the Strait of Sicily in July 2000. Sorting revealed that 1258 out of the 4098 fish larvae identified belonged to mesopelagic species; Cyclothone braueri (67.6% of the total), Electrona Risso (7.8%) and Myctophum punctatum (7.7%) were the most prevalent species, with 850, 97, and 98 individuals, respectively. The surface density patterns of mesopelagic fish larvae appear to be related to the hydrographic characteristics and structures determined by the surface circulation path. [ABSTRACT FROM AUTHOR]

The European Anchovy (Engraulis encrasicolus, Linnaeus, 1758) represents one of the most important fishery resources in some areas of the Mediterranean. This short-lived, small pelagic fish is characterized by large interannual fluctuations, probably as a result of environmental variability. As part of the European Project Med 98-070, the main aim of which was the study of the anchovy population in the Strait of Sicily, icthyoplankton surveys were carried out between 1999 and 2001, during the peak spawning season for anchovy. Present work reports the relationship between meso-zooplankton biomass and the abundance of anchovy eggs and larvae in the Strait of Sicily. Data on anchovy egg abundance showed that the main spawning area was located in the north-western region of the study area. The branch of the Atlantic Ionian Stream, running parallel to the southern Sicilian coast, acts as a transport mechanism for anchovy eggs and larvae towards the southernmost end of the island, off Cape Passero. Observed distributions were largely consistent with local hydrographic features, which allow larvae to be retained in areas providing the necessary feeding conditions for recruitment success. [ABSTRACT FROM AUTHOR]

Vascular endothelial growth factor (VEGF) is a major mediator in angiogenesis and vascular permeability. In central nervous system (CNS) it plays a pivotal role as: 1. inductor of endothelial cell proliferation, migration and inhibition of apoptosis, and 2. mediator of vascular permeability and subsequently of brain edema. This ubiquitous epiphenomenon is a major complication in several CNS pathologies, including head trauma and stroke. After brain injury the expression of VEGF is increased contributing to disruption of the blood brain barrier (BBB). VEGF increase the permeability of BBB via the synthesis/release of nitric oxide and subsequent activation of soluble guanylate cyclase. The immunohistochemistry shows an increase of stained astrocytes and endothelial cells around cortical micronecrosis. VEGF immunopositivity distribution shows some correspondence with the blood brain barrier breakdown following a cortical micronecrosis. [ABSTRACT FROM AUTHOR]

In this paper we give some characterizations of p-constrainedness, p a prime, and relate it to questions concerning Frattini chief factors of a finite group G and irreducible components of the second term of the lower Loewy series of the principal indecomposable projective $ \Bbb F_p G$ -module. [ABSTRACT FROM AUTHOR]

The growth of solid tumors is highly dependent on vascular proliferation. Vascular endothelial growth factor (VEGF), the main mediator of angiogenesis, and platelet-derived growth factor receptor-β (PDGFR-β), receptor for the potent mitogen PDGF, are two indicators of the angiogenic potential of human gliomas. We studied a series of 57 surgical biopsies of astrocytic neoplasms by immunohistochemistry to elucidate the relationship between tumor proliferation, quantified as Ki67-LI, and the expression of these two proteins. Ki67-LI increases throughout histological malignancy, although staining in endothelial cells has rarely been recorded. Elevated amounts of VEGF-positive tumor cells (VEGF-LI) were found in anaplastic astrocytomas and glioblastomas, mainly around areas of necrosis, cysts, or edema. Endothelium of blood vessels was consistently stained. PDGFR-β positivity was found in glomeruloid formations and in tumor cells, excluding pilocytic astrocytomas. Multinucleated giant cells and perivascular tumor cells were positive in glioblastomas. In addition, peritumoral microglia-like cells were also stained in some cases. Statistical correlation was only found between PDGFR-β and Ki67 LIs. In conclusion, VEGF as permeability factor is involved in the development of secondary neoplastic changes, whereas PDGFR-β is directly correlated to proliferation indexes. Strong expression of VEGF and PDGFR-β found in endothelium and tumor cells would seem to support a combined role in tumoral neoangiogenesis [ABSTRACT FROM AUTHOR]

In this paper we obtain an effective algorithm to compute all even orders and ramification indices of homeomorphisms of finite order acting on compact surfaces, orientable or not. This completes the case of odd orders, previously studied by the authors. [ABSTRACT FROM AUTHOR]

In this paper we get an effective algorithm to compute all odd orders and ramification indices of homeomorphisms acting on compact surfaces, orientable or not. [ABSTRACT FROM AUTHOR]

Objective: To assess the diagnostic value of the relationship between subcutaneous tumors and the superficial fascia in the characterization of soft-tissue masses.Design: MR studies of 64 soft tissue masses located in the subcutaneous space were reviewed. We established five grades of relationship between tumors and superficial fascia and analyzed the probability of the lesions in each group being malignant. Group 1 tumors did not contact the fascia; group 2 lesions contacted it slightly, with acute angles between the tumor and the fascia; group 3 lesions had wider contact with larger acute or right angles; group 4 tumors had even wider contact with obtuse angles with the fascia; and group 5 was composed of lesions that crossed the superficial fascia.Results: The probability of a subcutaneous lesion that crosses the superficial fascia being malignant was 6.88 times greater than for lesions that did not cross the fascia. For lesions forming obtuse angles with the fascia the probability of malignancy was 6.3 times greater than that of tumors that did not present this sign. All histologically verified fascial infiltrations occurred in malignant lesions of groups 4 and 5.Conclusions: Malignant tumors of the subcutaneous compartment have a higher tendency to develop a close relationship with the fascia than benign lesions. Obtuse angles between superficial fascia and a subcutaneous mass or a lesion crossing the fascia strongly suggest malignancy. [ABSTRACT FROM AUTHOR]

Objective: The imaging characteristics of lipoma arborescens using plain radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) are described.Design and Patients: Five patients with a diagnosis of lipoma arborescens are presented. Three had monoarticular involvement of the knee joint. In the remaining two patients both knees and both hips, respectively, were affected. All patients were examined using plain radiographs and MRI. CT was employed in two cases.Results and Conclusions: A conclusive diagnosis with exclusion of other synovial pathologies having similar clinical and radiological behavior can be achieved on the basis of the MRI characteristics of lipoma arborescens. The aetiology of lipoma arborescens remains unknown, but its association with previous pathology of the affected joints in all our patients supports the theory of a non-neoplastic reactive process involving the synovial membrane. [ABSTRACT FROM AUTHOR]

The most favorable type of traumatic intracranial bleeding in childhood is the extradural hemorrage (EDH). The posterior fossa location is less frequent than the supratentorial site. In the period from January 1989 to January 1994 we treated 2,372 patients with craniocerebral trauma; 31 had extradural hematomas (1.3%); 3 of them were located in the posterior fossa (9.7%): 1 boy and 2 girls aged from 6 to 16 years. The traumatic mechanism was an occipital fall in all cases. Diagnosis was made by computed tomography scan (CT). Two of them had a rapidly deteriorating course. The three patients were operated on without mortality and there was no morbidity. The role of CT in the early detection of lesions and prompt surgical evacuation may reduce the mortality and morbidity from this lesion. The interaction between these factors is discussed. [ABSTRACT FROM AUTHOR]

Once the existence of metrizable (LF)-spaces was discovered, the problem whether the completion of an (LF)-space is or is not an (LF)-space was answered in the negative, because no (LF)-space can be a Fréchet space. However, some (non-metrizable) (LF)-spaces are complete, e.g. the classical Köthe's strict (LF)-spaces. In this paper we will carry out a thorough study of the completeness of (LF)-spaces stressing upon the stable completion properties of (LB)-spaces. A basic tool for handling this problem is an Open Mapping Theorem for completions of (LF)-spaces, which is also proved in the present paper. [ABSTRACT FROM AUTHOR]

An automated system for on-line measurement of enzyme activity is proposed. The system uses a flow injection manifold in the stopped-flow mode to measure initial reaction rates. The time during which the flow is halted is selected in such a way as to optimise the enzyme/substrate ratio for the correct determination of activity values. The proposed system was used to determine the activity of laccase produced by the fungus Trametes versicolor immobilised on nylon in a fixed-bed reactor used for treating pulp mill waste water. [ABSTRACT FROM AUTHOR]

The production of lipase by Candida rugosa in batch cultures was studied. The initial concentration of the carbon source employed, oleic acid, had an important effect on the final lipolytic activity levels. The maximum lipase/substrate yield and specific productivity obtained correspond to an initial oleic acid concentration of 2 g/l. At higher concentrations, up to 8 g/l oleic acid, specific productivity decreased. Lipase production was not observed below 1 g/l oleic acid. Lipase inactivation in culture broth due to surface forces and shear stress at the gas/liquid interface was not observed. There was no shear stress denaturation at stirring rates of 250, 500 and 750 rpm. No temperature inactivation was detected up to 50° C. Two different lipases with a similar molecular weight of 60kDa were purified from culture broth. [ABSTRACT FROM AUTHOR]

A 57-year-old 132-kg female (BMI 48.6) with endstage cardiac failure is presented. Because of a progressive cardiomyopathy, the patient required a heart transplant. However, before receiving the transplant, major weight loss was deemed to be mandatory.Supervised dieting had manifestly failed, and thus a highly effective weight-reducing operation, biliopancreatic diversion, was performed. This resulted in a weight loss of 50.4 kg in 9 months. She then underwent successful cardiac transplantation, and progressed well for several months. She then developed severe psychiatric depression, withheld her medications and developed a lethal acute rejection phenomenon. [ABSTRACT FROM AUTHOR]

The authors present a case of tumor thrombus in the inferior vena cava produced by angiomyolipoma in a young woman with tuberous sclerosis. Diagnosis was made by computed tomography (CT) by measuring the attenuation values of the tumor thrombus. The values obtained were characteristic of fat, demonstrating that tumoral invasion was the cause of the thrombus. To our knowledge, this is the first description of such an association shown by CT in the literature. [ABSTRACT FROM AUTHOR]

The notion of L-boundary, a new causal boundary proposed by R. Low based on constructing a 'sky at infinity' for any light ray, is discussed in detail. The analysis of the notion of L-boundary will be done in the 3-dimensional situation for the ease of presentation. The proposed notion of causal boundary is intrinsically conformal and, as it will be proved in the paper, under natural conditions provides a natural extension M¯ of the given spacetime M with smooth boundary ∂M=M¯\M. The extensions M¯ of any conformal manifold M constructed in this way are characterised exclusively in terms of local properties at the boundary points. Such extensions are called L-extensions and it is proved that, if they exist, they are essentially unique. Finally it is shown that in the 3-dimensional case, any L-extension is equivalent to the canonical extension obtained by using the L-boundary of the manifold. [ABSTRACT FROM AUTHOR]

The authors found a terrible mistake in the manuscript. The legends from the Fig. 5 and 6 are interchanged. The Fig. 5 should be appeared with the legend from the Fig. 6 and Fig. 6 should be appeared with the legend from the Fig. 5. [ABSTRACT FROM AUTHOR]