Safety and operability of small fishing vessels: study of a series of stability-related accidents

The intact stability of five small Spanish fishing vessels with ages between 3 and 8 years old which sunk in stability related accidents between 2004 and 2007 is compared to the stability of the fishing vessels which were retired from service to build those. The seakeeping performance of both sets of vessels is also compared. The differences found between the results obtained by the two methods have been analyzed. The suitability of seakeeping methods to assess stability performance is discussed.

Fishing effort control regulations influence on stability, safety and operability of small fishing vessels: study of a series of stability related accidents occurred in Spain between 2004 and 2007

Entre los años 2004 y 2007 se hundieron por problemas de estabilidad cinco pesqueros españoles de pequeña eslora, de características parecidas, de relativamente poca edad, que habían sido construidos en un intervalo de pocos años. La mayoría de los tripulantes de esos pesqueros fallecieron o desaparecieron en esos accidentes. Este conjunto de accidentes tuvo bastante repercusión social y mediática. Entre ingenieros navales y marinos del sector de la pesca se relacionó estos accidentes con los condicionantes a los diseños de los pesqueros impuestos por la normativa de control de esfuerzo pesquero. Los accidentes fueron investigados y publicados sus correspondientes informes; en ellos no se exploró esta supuesta relación. Esta tesis pretende investigar la relación entre esos accidentes y los cambios de la normativa de esfuerzo pesquero. En la introducción se expone la normativa de control de esfuerzo pesquero analizada, se presentan datos sobre la estructura de la flota pesquera en España y su accidentalidad, y se detallan los criterios de estabilidad manejados durante el trabajo, explicando su relación con la seguridad de los pesqueros. Seguidamente se realiza un análisis estadístico de la siniestralidad en el sector de la pesca para establecer si el conjunto de accidentes estudiados supone una anomalía, o si por el contrario el conjunto de estos accidentes no es relevante desde el punto de vista estadístico. Se analiza la siniestralidad a partir de diversas bases de datos de buques pesqueros en España y se concluye que el conjunto de accidentes estudiados supone una anomalía estadística, ya que la probabilidad de ocurrencia de los cinco sucesos es muy baja considerando la frecuencia estimada de pérdidas de buques por estabilidad en el subsector de la flota pesquera en el que se encuadran los cinco buques perdidos. A continuación el trabajo se centra en la comparación de los buques accidentados con los buques pesqueros dados de baja para construir aquellos, según exige la normativa de control de esfuerzo pesquero; a estos últimos buques nos referiremos como “predecesores” de los buques accidentados. Se comparan las dimensiones principales de cada buque y de su predecesor, resultando que los buques accidentados comparten características de diseño comunes que son sensiblemente diferentes en los buques predecesores, y enlazando dichas características de diseño con los requisitos de la nueva normativa de control del esfuerzo pesquero bajo la que se construyeron estos barcos. Ello permite establecer una relación entre los accidentes y el mencionado cambio normativo. A continuación se compara el margen con que se cumplían los criterios reglamentarios de estabilidad entre los buques accidentados y los predecesores, encontrándose que en cuatro de los cinco casos los predecesores cumplían los criterios de estabilidad con mayor holgura que los buques accidentados. Los resultados obtenidos en este punto permiten establecer una relación entre el cambio de normativa de esfuerzo pesquero y la estabilidad de los buques. Los cinco buques accidentados cumplían con los criterios reglamentarios de estabilidad en vigor, lo que cuestiona la relación entre esos criterios y la seguridad. Por ello se extiende la comparativa entre pesqueros a dos nuevos campos relacionados con la estabilidad y la seguridad delos buques: • Movimientos a bordo (operatividad del buque), y • Criterios de estabilidad en condiciones meteorológicas adversas El estudio de la operatividad muestra que los buques accidentados tenían, en general, una mayor operatividad que sus predecesores, contrariamente a lo que sucedía con el cumplimiento de los criterios reglamentarios de estabilidad. Por último, se comprueba el desempeño de los diez buques en dos criterios específicos de estabilidad en caso de mal tiempo: el criterio IMO de viento y balance intenso, y un criterio de estabilidad de nueva generación, incluyendo la contribución original del autor de considerar agua en cubierta. Las tendencias observadas en estas dos comparativas son opuestas, lo que permite cuestionar la validez del último criterio sin un control exhaustivo de los parámetros de su formulación, poniendo de manifiesto la necesidad de más investigaciones sobre ese criterio antes de su adopción para uso regulatorio. El conjunto de estos resultados permite obtener una serie de conclusiones en la comparativa entre ambos conjuntos de buques pesqueros. Si bien los resultados de este trabajo no muestran que la aprobación de la nueva normativa de esfuerzo pesquero haya significado una merma general de seguridad en sectores enteros de la flota pesquera, sí se concluye que permitió que algunos diseños de buques pesqueros, posiblemente en busca de la mayor eficiencia compatible con dicha normativa, quedaran con una estabilidad precaria, poniendo de manifiesto que la relación entre seguridad y criterios de estabilidad no es unívoca, y la necesidad de que éstos evolucionen y se adapten a los nuevos diseños de buques pesqueros para continuar garantizando su seguridad. También se concluye que la estabilidad es un aspecto transversal del diseño de los buques, por lo que cualquier reforma normativa que afecte al diseño de los pesqueros o su forma de operar debería estar sujeta a evaluación por parte de las autoridades responsables de la seguridad marítima con carácter previo a su aprobación. ABSTRACT Between 2004 and 2007 five small Spanish fishing vessels sank in stability related accidents. These vessels had similar characteristics, had relatively short age, and had been built in a period of a few years. Most crewmembers of these five vessels died or disappeared in those accidents. This set of accidents had significant social and media impact. Among naval architects and seamen of the fishing sector these accidents were related to the design constraints imposed by the fishing control effort regulations. The accidents were investigated and the official reports issued; this alleged relationship was not explored. This thesis aims to investigate the relationship between those accidents and changes in fishing effort control regulations. In the introduction, the fishing effort control regulation is exposed, data of the Spanish fishing fleet structure and its accident rates are presented, and stability criteria dealt with in this work are explained, detailing its relationship with fishing vessel safety. A statistical analysis of the accident rates in the fishing sector in Spain is performed afterwards. The objective is determining whether the set of accidents studied constitute an anomaly or, on the contrary, they are not statistically relevant. Fishing vessels accident rates is analyzed from several fishing vessel databases in Spain. It is concluded that the set of studied accidents is statistically relevant, as the probability of occurrence of the five happenings is extremely low, considering the loss rates in the subsector of the Spanish fishing fleet where the studied vessels are fitted within. From this point the thesis focuses in comparing the vessels lost and the vessels that were decommissioned to build them as required by the fishing effort control regulation; these vessels will be referred to as “predecessors” of the sunk vessels. The main dimensions between each lost vessel and her predecessor are compared, leading to the conclusion that the lost vessels share design characteristics which are sensibly different from the predecessors, and linking these design characteristics with the requirements imposed by the new fishing control effort regulations. This allows establishing a relationship between the accidents and this regulation change. Then the margin in fulfilling the regulatory stability criteria among the vessels is compared, resulting, in four of the five cases, that predecessors meet the stability criteria with greater clearance than the sunk vessels. The results obtained at this point would establish a relationship between the change of fishing effort control regulation and the stability of vessels. The five lost vessels complied with the stability criteria in force, so the relation between these criteria and safety is put in question. Consequently, the comparison among vessels is extended to other fields related to safety and stability: • Motions onboard (operability), and • Specific stability criteria in rough weather The operability study shows that the lost vessels had in general greater operability than their predecessors, just the opposite as when comparing stability criteria. Finally, performance under specific rough weather stability criteria is checked. The criteria studied are the IMO Weather Criterion, and one of the 2nd generation stability criteria under development by IMO considering in this last case the presence of water on deck, which is an original contribution by the author. The observed trends in these two cases are opposite, allowing to put into question the last criterion validity without an exhaustive control of its formulation parameters; indicating that further research might be necessary before using it for regulatory purposes. The analysis of this set of results leads to some conclusions when comparing both groups of fishing vessels. While the results obtained are not conclusive in the sense that the entry into force of a new fishing effort control in 1998 caused a generalized safety reduction in whole sectors of the Spanish fishing fleet, it can be concluded that it opened the door for some vessel designs resulting with precarious stability. This evidences that the relation between safety and stability criteria is not univocal, so stability criteria needs to evolve for adapting to new fishing vessels designs so their safety is still guaranteed. It is also concluded that stability is a transversal aspect to ship design and operability, implying that any legislative reform affecting ship design or operating modes should be subjected to assessing by the authorities responsible for marine safety before being adopted.

Regulation of transport pathways in tumor vessels: Role of tumor type and microenvironment

Novel anti-neoplastic agents such as gene targeting vectors and encapsulated carriers are quite large (approximately 100–300 nm in diameter). An understanding of the functional size and physiological regulation of transvascular pathways is necessary to optimize delivery of these agents. Here we analyze the functional limits of transvascular transport and its modulation by the microenvironment. One human and five murine tumors including mammary and colorectal carcinomas, hepatoma, glioma, and sarcoma were implanted in the dorsal skin-fold chamber or cranial window, and the pore cutoff size, a functional measure of transvascular gap size, was determined. The microenvironment was modulated: (i) spatially, by growing tumors in subcutaneous or cranial locations and (ii) temporally, by inducing vascular regression in hormone-dependent tumors. Tumors grown subcutaneously exhibited a characteristic pore cutoff size ranging from 200 nm to 1.2 μm. This pore cutoff size was reduced in tumors grown in the cranium or in regressing tumors after hormone withdrawal. Vessels induced in basic fibroblast growth factor-containing gels had a pore cutoff size of 200 nm. Albumin permeability was independent of pore cutoff size. These results have three major implications for the delivery of therapeutic agents: (i) delivery may be less efficient in cranial tumors than in subcutaneous tumors, (ii) delivery may be reduced during tumor regression induced by hormonal ablation, and (iii) permeability to a molecule is independent of pore cutoff size as long as the diameter of the molecule is much less than the pore diameter.

A physiologic function for p-glycoprotein (MDR-1) during the migration of dendritic cells from skin via afferent lymphatic vessels

P-glycoprotein (MDR-1) is a well-known transporter that mediates efflux of chemotherapeutic agents from the intracellular milieu and thereby contributes to drug resistance. MDR-1 also is expressed by nonmalignant cells, including leukocytes, but physiologic functions for MDR-1 are poorly defined. Using an initial screening assay that included >100 mAbs, we observed that neutralizing mAbs MRK16, UIC2, and 4E3 against MDR-1 specifically and potently blocked basal-to-apical transendothelial migration of mononuclear phagocytes, a process that may mimic their migration into lymphatic vessels. Antagonists of MDR-1 then were used in a model of authentic lymphatic clearance. In this model, antigen-presenting dendritic cells (DC) migrate out of explants of cultured human skin and into the culture medium via dermal lymphatic vessels. DC and T cells derived from skin expressed MDR-1 on their surfaces. Addition of anti-MDR-1 mAbs MRK16, UIC2, or the MDR-1 antagonist verapamil to skin explants at the onset of culture inhibited the appearance of DC, and accompanying T cells, in the culture medium by approximately 70%. Isotype-matched control mAbs against other DC molecules including CD18, CD31, and major histocompatibility complex I did not block. In the presence of MDR-1 antagonists, epidermal DC were retained in the epidermis, in contrast to control conditions. In summary, this work identifies a physiologic function for MDR-1 during the mobilization of DC and begins to elucidate how these critical antigen-presenting cells migrate from the periphery to lymph nodes to initiate T lymphocyte-mediated immunity.

Conditional switching of vascular endothelial growth factor (VEGF) expression in tumors: Induction of endothelial cell shedding and regression of hemangioblastoma-like vessels by VEGF withdrawal

We have recently shown that VEGF functions as a survival factor for newly formed vessels during developmental neovascularization, but is not required for maintenance of mature vessels. Reasoning that expanding tumors contain a significant fraction of newly formed and remodeling vessels, we examined whether abrupt withdrawal of VEGF will result in regression of preformed tumor vessels. Using a tetracycline-regulated VEGF expression system in xenografted C6 glioma cells, we showed that shutting off VEGF production leads to detachment of endothelial cells from the walls of preformed vessels and their subsequent death by apoptosis. Vascular collapse then leads to hemorrhages and extensive tumor necrosis. These results suggest that enforced withdrawal of vascular survival factors can be applied to target preformed tumor vasculature in established tumors. The system was also used to examine phenotypes resulting from over-expression of VEGF. When expression of the transfected VEGF cDNA was continuously “on,” tumors became hyper-vascularized with abnormally large vessels, presumably arising from excessive fusions. Tumors were significantly less necrotic, suggesting that necrosis in these tumors is the result of insufficient angiogenesis.

Localization of neuropeptide Y Y1 receptors in cerebral blood vessels

The localization of neuropeptide Y (NPY) Y1 receptor (R) -like immunoreactivity (LI) has been studied in cerebral arteries and arterioles of the rat by immunohistochemistry using fluorescence, confocal, and electron microscopy. High levels of Y1-R-LI were observed in smooth muscle cells (SMCs) in the small arterioles of the pial arterial network, especially on the basal surface of the brain, and low levels in the major basal cerebral arteries. The levels of Y1-R-LI varied strongly between adjacent SMCs. Y1-R-LI was associated with small endocytosis vesicles, mainly on the outer surface of the SMCs, but also on their endothelial side and often laterally at the interface between two SMCs. NPY-immunoreactive (Ir) nerve fibers could not be detected in association with the Y1-R-rich small arterioles but only around arteries with low Y1-R levels. A dense network of central NPY-Ir nerve fibers in the superficial layers of the brain was lying close to the strongly Y1-R-Ir small arterioles. The results indicate that NPY has a profound effect on small arterioles of the brain acting on Y1-Rs, both on the peripheral and luminal side of the SMCs. However, the source of the endogenous ligand, NPY, remains unclear. NPY released from central neurons may play a role, in addition to blood-borne NPY.

Polycystin 1 is required for the structural integrity of blood vessels

Autosomal dominant polycystic kidney disease (ADPKD), often caused by mutations in the PKD1 gene, is associated with life-threatening vascular abnormalities that are commonly attributed to the frequent occurrence of hypertension. A previously reported targeted mutation of the mouse homologue of PKD1 was not associated with vascular fragility, leading to the suggestion that the vascular lesion may be of a secondary nature. Here we demonstrate a primary role of PKD1 mutations in vascular fragility. Mouse embryos homozygous for the mutant allele (Pkd1L) exhibit s.c. edema, vascular leaks, and rupture of blood vessels, culminating in embryonic lethality at embryonic day 15.5. Kidney and pancreatic ductal cysts are present. The Pkd1-encoded protein, mouse polycystin 1, was detected in normal endothelium and the surrounding vascular smooth muscle cells. These data reveal a requisite role for polycystin 1 in maintaining the structural integrity of the vasculature as well as epithelium and suggest that the nature of the PKD1 mutation contributes to the phenotypic variance in ADPKD.

Visualization of Cavitated Vessels in Winter and Refilled Vessels in Spring in Diffuse-Porous Trees by Cryo-Scanning Electron Microscopy1

Xylem cavitation in winter and recovery from cavitation in the spring were visualized in two species of diffuse-porous trees, Betula platyphylla var. japonica Hara and Salix sachalinensis Fr. Schm., by cryo-scanning electron microscopy after freeze-fixation of living twigs. Water in the vessel lumina of the outer three annual rings of twigs of B. platyphylla var. japonica and of S. sachalinensis gradually disappeared during the period from January to March, an indication that cavitation occurs gradually in these species during the winter. In April, when no leaves had yet expanded, the lumina of most of the vessels of both species were filled with water. Many vessel lumina in twigs of both species were filled with water during the period from the subsequent growth season to the beginning of the next winter. These observations indicate that recovery in spring occurs before the onset of transpiration and that water transport through twigs occurs during the subsequent growing season. We found, moreover, that vessels repeat an annual cycle of winter cavitation and spring recovery from cavitation for several years until irreversible cavitation occurs.

Specific accumulation of tumor-derived adhesion factor in tumor blood vessels and in capillary tube-like structures of cultured vascular endothelial cells.

Tumor-derived adhesion factor (TAF) was previously identified as a cell adhesion molecule secreted by human bladder carcinoma cell line EJ-1. To elucidate the physiological function of TAF, we examined its distribution in human normal and tumor tissues. Immunochemical staining with an anti-TAF monoclonal antibody showed that TAF was specifically accumulated in small blood vessels and capillaries within and adjacent to tumor nests, but not in those in normal tissues. Tumor blood vessel-specific staining of TAF was observed in various human cancers, such as esophagus, brain, lung, and stomach cancers. Double immunofluorescent staining showed apparent colocalization of TAF and type IV collagen in the vascular basement membrane. In vitro experiments demonstrated that TAF preferentially bound to type IV collagen among various extracellular matrix components tested. In cell culture experiments, TAF promoted adhesion of human umbilical vein endothelial cells to type IV collagen substrate and induced their morphological change. Furthermore, when the endothelial cells were induced to form capillary tube-like structures by type I collagen, TAF and type IV collagen were exclusively detected on the tubular structures. The capillary tube formation in vitro was prevented by heparin, which inhibited the binding of TAF to the endothelial cells. These results strongly suggest that TAF contributes to the organization of new capillary vessels in tumor tissues by modulating the interaction of endothelial cells with type IV collagen.

Exogenous vascular endothelial growth factor induces malformed and hyperfused vessels during embryonic neovascularization.

Vascular endothelial growth factor (VEGF) is a potent and specific endothelial mitogen that is able to induce angiogenesis in vivo [Leung, D. W., Cachianes, G., Kuang, W.-J., Goeddel, D. V. & Ferrara, N. (1989) Science 246 1306-1309]. To determine if VEGF also influences the behavior of primordial endothelial cells, we used an in vivo vascular assay based on the de novo formation of vessels. Japanese quail embryos injected with nanomolar quantities of the 165-residue form of VEGF at the onset of vasculogenesis exhibited profoundly altered vessel development. In fact, the overall patterning of the vascular network was abnormal in all VEGF-injected embryos. The malformations were attributable to two specific endothelial cell activities: (i) inappropriate neovascularization in normally avascular areas and (ii) the unregulated, excessive fusion of vessels. In the first instance, supernumerary vessels directly linked the inflow channel of the heart to the aortic outflow channel. The second aberrant activity led to the formation of vessels with abnormally large lumens. Ultimately, unregulated vessel fusion generated massive vascular sacs that obliterated the identity of individual vessels. These observations show that exogenous VEGF has an impact on the behavior of primordial endothelial cells engaged in vasculogenesis, and they strongly suggest that endogenous VEGF is important in vascular patterning and regulation of vessel size (lumen formation).