72 research outputs found
A Chiral Spin Theory in the Framework of an Invariant Evolution Parameter Formalism
We present a formulation for the construction of first order equations which
describe particles with spin, in the context of a manifestly covariant
relativistic theory governed by an invariant evolution parameter; one obtains a
consistent quantized formalism dealing with off-shell particles with spin. Our
basic requirement is that the second order equation in the theory is of the
Schr\"{o}dinger-Stueckelberg type, which exhibits features of both the
Klein-Gordon and Schr\"{o}dinger equations. This requirement restricts the
structure of the first order equation, in particular, to a chiral form. One
thus obtains, in a natural way, a theory of chiral form for massive particles,
which may contain both left and right chiralities, or just one of them. We
observe that by iterating the first order system, we are able to obtain second
order forms containing the transverse and longitudinal momentum relative to a
time-like vector used to maintain covariance of the theory.
This time-like vector coincides with the one used by Horwitz, Piron, and Reuse
to obtain an invariant positive definite space-time scalar product, which
permits the construction of an induced representation for states of a particle
with spin. We discuss the currents and continuity equations, and show that
these equations of motion and their currents are closely related to the spin
and convection parts of the Gordon decomposition of the Dirac current. The
transverse and longitudinal aspects of the particle are complementary, and can
be treated in a unified manner using a tensor product Hilbert space.
Introducing the electromagnetic field we find an equation which gives rise to
the correct gyromagnetic ratio, and is fully Hermitian under the proposed
scalar product. Finally, we show that the original structure of Dirac'sComment: Latex, 61 pages. Minor revisions. To be published in J. Math. Phy
Earliest cranio-encephalic trauma from the Levantine Middle Palaeolithic: 3D reappraisal of the Qafzeh 11 skull, consequences of pediatric brain damage on individual life condition and social care.
The Qafzeh site (Lower Galilee, Israel) has yielded the largest Levantine hominin collection from Middle Palaeolithic layers which were dated to circa 90-100 kyrs BP or to marine isotope stage 5b-c. Within the hominin sample, Qafzeh 11, circa 12-13 yrs old at death, presents a skull lesion previously attributed to a healed trauma. Three dimensional imaging methods allowed us to better explore this lesion which appeared as being a frontal bone depressed fracture, associated with brain damage. Furthermore the endocranial volume, smaller than expected for dental age, supports the hypothesis of a growth delay due to traumatic brain injury. This trauma did not affect the typical human brain morphology pattern of the right frontal and left occipital petalia. It is highly probable that this young individual suffered from personality and neurological troubles directly related to focal cerebral damage. Interestingly this young individual benefited of a unique funerary practice among the south-western Asian burials dated to Middle Palaeolithic
Identité biologique des artisans moustériens de Kebara (Mont Carmel, Israël) Réflexions sur le concept de néanderthalien au Levant méditerranéen
Dès les premières découvertes de fossiles humains provenant du Bassin Méditerranéen oriental et datés du Pléistocène supérieur, il est apparu évident que la documentation anthropologique illustrait une hétérogénéité biologique, suscitant des interprétations différentes. Par la suite, l’enrichissement de la documentation avec de nouvelles fouilles est venu alimenter, au sein de la communauté scientifique, les discussions portant aussi bien sur les affinités phylogénétiques des fossiles que sur leur position chronologique. La prise en compte, sur ces fossiles proche-orientaux, de l’originalité de l’assemblage de caractères anatomiques présents ne doit pas être sous-estimée pour une meilleure évaluation des composantes régionales. C’est ce qui est proposé à propos de Kebara, l’objectif étant de favoriser une approche cohérente de la diversité biologique des hommes du Paléolithique moyen dans la région, qui n’exclut pas les influences extra-européennes.The southern Mediterranean Levant has attracted the attention of the scientific community since the early excavations conducted at the beginning of the 20th century on several sites, which provided a significant sample of Upper Pleistocene hominids. Additional skeletal material, circumscribed geographically and chronologically, raises several questions concerning the biological differences and similarities between the hominid samples represented, and their geographical position at the crossroads of Africa and Eurasia. The excellent state of preservation of the hominid remains enables a new insight into the anatomy of Levantine Middle Palaeolithic populations and provides important data for reconstructing the pattern of human evolution in the Near East. With this in view, re-examination of some skeletal remains recovered at Kebara Cave suggests. that biological differences and similarities may have existed between Neanderthals and Levantine Middle Palaeolithic hominids, strengthening the existence of regional variation
Влияние глобальных климатических изменений на размеры косточек среднего уха
Department of Anatomy and Anthropology Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel, Department of Otorhinolaryngology Head Neck Surgery, The Sheba Medical Center, Tel-Hashomer, Conferinţa Știinţifică Internaţională ”Probleme actuale ale morfologiei” dedicată сentenarului profesorului B.Z. Perlin, Chişinău, 20-22 septembrie 2012Abstract
Hypothesis: The morphology of middle ear ossicles varies between people living in different climatic regions.
Background: The differences between climatic conditions in different world regions have a morphological and physiological influence on human development. The present study is aimed to investigate morphological variations of middle-ear
ossicles collected from different geographic locations on the globe. Methods: Middle ear ossicles (total samples 631) were
collected from 6 different geographic regions: Australia, Chile, France, India, Israel and Kenya. Latitude and longitude,
and climatic parameters (mean temperature, humidity and daylight duration of the warmer and colder months, and altitude
above sea level) were collected for each region. The associations between middle ear ossicles’ dimensions and climate were
evaluated using Pearson’s correlations. Results: Significant differences between samples of middle ear ossicles’ characteristics were found. Correlations between the ‘above sea level’ altitude and longitudinal sizes of the malleus, incus and
stapes were negative. Correlations between warm temperature and longitudinal sizes of the malleus, incus and stapes were
positive. Conclusions: Differences in characteristics of middle ear ossicles encountered between territorial samples could
be the result of climatic variations.
Гипотеза: морфология косточек среднего уха отличается у людей, живущих в различных климатических районах.
Справочная информация: различия климатических условий в различных регионах мира имеют морфологические и
физиологические воздействие на развитие человека. Данное исследование направлено на исследование морфологических изменений косточек среднего уха, собранных в различных географических точках земного шара. Методы:
косточки среднего уха (всего 631 образец) были собраны в 6 различных географических регионах: Австралия, Чили,
Франция, Индия, Израиль и Кения. Широта и долгота, климатические параметры (средняя температура, влажность
и продолжительность светового дня теплых и холодных месяцев, высота над уровнем моря) были определены для
каждого региона. Связь между размерами косточек среднего уха и климатом были оценены с использованием корреляции Пирсона. Результат: были найдены значительные различия в характеристиках образцов косточек среднего
уха. Корреляция между «над уровнем моря» и продольными размерами молоточка, наковальни и стремечка были
обратнопропорциональными. Корреляция между теплой температурой и продольными размерами слуховых косточек
были прямопропорциональными. Выводы: Различия в характеристиках косточек среднего уха различных территориальных образцов могут быть результатом климатических изменений
Bone marrow mesenchymal stem cells do not enhance intra-synovial tendon healing despite engraftment and homing to niches within the synovium
Intra-synovial tendon injuries display poor healing, which often results in reduced functionality and pain. A lack of effective therapeutic options has led to experimental approaches to augment natural tendon repair with autologous mesenchymal stem cells (MSCs) although the effects of the intra-synovial environment on the distribution, engraftment and functionality of implanted MSCs is not known. This study utilised a novel sheep model which, although in an anatomically different location, more accurately mimics the mechanical and synovial environment of the human rotator cuff, to determine the effects of intra-synovial implantation of MSCs
Persistent Place-Making in Prehistory: the Creation, Maintenance, and Transformation of an Epipalaeolithic Landscape
Most archaeological projects today integrate, at least to some degree, how past people engaged with their surroundings, including both how they strategized resource use, organized technological production, or scheduled movements within a physical environment, as well as how they constructed cosmologies around or created symbolic connections to places in the landscape. However, there are a multitude of ways in which archaeologists approach the creation, maintenance, and transformation of human-landscape interrelationships. This paper explores some of these approaches for reconstructing the Epipalaeolithic (ca. 23,000–11,500 years BP) landscape of Southwest Asia, using macro- and microscale geoarchaeological approaches to examine how everyday practices leave traces of human-landscape interactions in northern and eastern Jordan. The case studies presented here demonstrate that these Epipalaeolithic groups engaged in complex and far-reaching social landscapes. Examination of the Early and Middle Epipalaeolithic (EP) highlights that the notion of “Neolithization” is somewhat misleading as many of the features we use to define this transition were already well-established patterns of behavior by the Neolithic. Instead, these features and practices were enacted within a hunter-gatherer world and worldview
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