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Abstract

The objective of this study was to measure myelination of frontal lobe changes in infants and young children. Twenty-four cases of infants and children (age range 12–121 months) were evaluated by a quantitative assessment of T2- weighted MR image features. Reliable quantitative changes between white and gray matter correlated with developmental age in a group of children with no neurological findings. Myelination appears to be an increasing exponential function with the greatest rate of change occurring over the first 3 years of life. The quantitative changes observed were in accordance with revious
qualitative judgments of myelination development. Children with periventricular leukomalacia (PVL) showed delays in achieving levels of myelination when compared to normal children and adjusted for chronological age. The quantitative measure of myelination development may prove to be useful in assessing the stages of development and helpful in the quantitative descriptions of white matter disorders such as PVL.

Introduction
The relations between brain development and behavior in human infants and young children are of interest to developmental psychologists. For example, there are changes in brain development that relate to the acquisition of perceptual and cognitive processes. Also of interest are developmental issues: how are the changes in myelination in the developing brain related to changes in social, emotional, and cognitive domains? Many of the changes in behavior, including social and emotional behavior, have been quantified; therefore, it would be useful to have a quantified measure of brain development to compare to the measures of behavior. A method of assessing developmental brain change is to assess the changing levels of myelination. One approach to assessing myelination is to view the stained samples of brain tissue from specimens. Histologic studies of myelination of the forebrain have found no myelinated fibers before the seventh fetal month. In the telencephalic division of the forebrain, myelinated fibers first appear in the white matter of the cerebral hemispheres in the tenth fetal month. In the supralimbic zone of the forebrain, which comprises the white matter of the cortical layers, the myelination of the subcortical white matter is synchronized with the myelination of cortical projections from the dorsolateral and posterior nuclei of thalamus. Read the rest of this entry »

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Structural Abnormalities in the Brains of Human Subjects Who Use Methamphetamine

We visualize, for the first time, the profile of structural deficits in the human brain associated with chronic methamphetamine (MA) abuse. Studies of human subjects who have used MA chronically have revealed deficits in dopaminergic and serotonergic systems and cerebral metabolic abnormalities. Using magnetic resonance imaging (MRI) and new computational brain-mapping techniques, we determined the pattern of structural brain alterations associated with chronic MA abuse in human subjects and related these deficits to cognitive impairment. We used high-resolution MRI and surface-based computational image analyses to map regional abnormalities in the cortex, hippocampus, white matter, and ventricles in 22 human subjects who usedMAand 21 age-matched, healthy controls. Cortical maps revealed severe gray-matter deficits in the cingulate, limbic, and paralimbic cortices ofMAabusers (averaging 11.3% below control;p-0.05). On average,MAabusers had 7.8% smaller hippocampal volumes than control subjects ( p-0.01; left, p-0.01; right, p-0.05) and significant white-matter hypertrophy (7.0%; p - 0.01). Hippocampal deficits were mapped and correlated with memory performance on a word-recall test ( p- 0.05). MRI-based maps suggest that chronic methamphetamine abuse causes a selective pattern of cerebral deterioration that contributes to impaired memory performance. MA may selectively damage the medial temporal lobe and, consistent with metabolic studies, the cingulate–limbic cortex, inducing neuroadaptation, neuropil reduction, or cell death. Prominent white-matter hypertrophy may result from altered myelination and adaptive glial changes, including gliosis secondary to neuronal damage. These brain substrates may help account for the symptoms of MA abuse, providing therapeutic targets for drug-induced brain injury.
Key words: methamphetamine; brain imaging; drug abuse; MRI; cortex; hippocampus; limbic system; memory introduction Methamphetamine (MA) abuse is a growing epidemic worldwide. Read the rest of this entry »

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Utilizarea robotilor industriali

Robotii se utilizeaza in toate domeniile activitatii umane. Ele urmaresc satisfacerea unor necesitati individuale, de grup sau sociale, realizand economia. Economia se imparte in sectoare si domenii.

Productia apare in toate sectoarele economiei si anume in sectoarele primare si secundare, productia materiala, iar in sectoarele tertiare preponderenta devine productia nemateriala si anume a serviciilor.
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Constructia modulara a robotilor

Constructia modulara este caracterizata prin:
• Structura sistematica care este compusa dintr-un grup de sisteme si dispozitive care formeaza cuple cinematice conducatoare. Structura sistemica prezinta avantajul ca furnizeaza informatiile necesare pentru analiza cinematica si dinamica a sistemelor de actionare si mecanic ale robotului. Ea prezinta dezavantajul, ca nu reflecta decat partial functiile sistemelor de rang inferior robotului si particularitatile constructive ale acestora.
• Structura functional-constructiva sau structura modulara este cu dispozitive de ghidare cu topologie seriala pentru a evidentia proprietatile functionale si constructive ale robotilor (modul de robot).
Modul al unui robot, este un subansamblu care este corelat cu una sau mai multe cuple cinematice ale dispozitivului de ghidare si cu efectorul final.

Modulul de robot corelat cu cupla cinematica conducatoare are partile “fixe” ale sistemului de actionare aferent cuplei cinematice conducatoare si traductoarelor / senzorilor, solidarizate cu structura de rezistenta a unuia dintre elemente (i sau i+1). Legatura dintre doua module vecine se realizeaza prin intermediul structurii de rezistenta a elementului i. In acest mod, intregul robot cu dispozitivul de ghidare in topologie seriala este de fapt constituit din “legarea in serie” a unui numar de module.

Modulul de robot corelat cu o singura cupla cinematica poarta o denumire care este definita dupa functia lui in cadrul robotului. Read the rest of this entry »

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STRUCTURA ROBOTULUI

Structura unui robot este, defapat, un sistem compus din mai multe subsisteme. Sistem este un ansamblu de parti componente, elemente, si legaturile dintre acestea. Elementele care compun acest sistem se numesc subsisteme. La randul lor subsistemele pot avea si ele subsisteme, din acest motiv exista o ierarhizare si anume sistemul principal se numeste sistem de rangul 1, subsistemele se numesc sisteme de rangul 2, etc.

Modul cum se compune un sistem din subsisteme si legaturile dintre aceste subsisteme definesc structura unui sistem. Aceasta compunere a sistemelor din subsisteme se evidentiaza prin scheme bloc, iar legaturile dintre subsisteme, prin matrici de cuplare (care definesc legaturile dintre “intrarile” si “iesirile”) si matrici de structura (care ne arata care subsisteme sunt in legatura).
Robotul este un sistem de rangul 1, si se aseamana, constructiv, cu sistemul unui om, la fel si subsistemele robotului.

Schema bloc al structuri unui robot este:
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1.2. Introducere. Clasificarea robotilor industriali conform I.S.O.

Robotul poate fi definit ca o instalatie pentru automatizarea operatiilor pe care in conditii “clasice” le realizeaza omul, cu mana sa, sub supravegherea ochiului, coordonarea ochi-mana realizandu-se de catre creier. Pe langa roboti, operatii de manipulare executa si manipulatoarele.

Din cele de mai sus putem realiza urmatoarele definitii:
o Robotul are o structura mecanica mai complexa (mai multe grade de mobilitate) si este condus dupa un program flexibil.
o Manipulatoarele au o structura mecanica mai simpla (mai putine grade de mobilitate) si este condus dupa un program rigid (greu modificabil).

Avem doua mari categorii de roboti :
- Ficsi, cei care sunt imobili fata de anumite componente ale mediului in care evolueaza
- Mobili, cei care se pot deplasa, folosind in acest scop:
- roti
- senile
- prin pasire
- tarare.
Vehiculele ghidate automat sunt roboti mobili, cu deplasare pe roti / senile. Read the rest of this entry »

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1.1. Robotica in istoria omenirii

Domeniul de stiinta Robotica si fenomenul “robot”, au aparut in cea de a doua jumatate a secolului XX. Aparitia lor se incadreaza in linia de evolutie a vietii si in acest cadru, a omenirii. Acest lucru se datoreaza cresterii productivitatii.


La inceputul omenirii actionarea asupra mediului se facea folosind energie biologica

Mai tarziu omul actioneaza cu ajutorul uneltelor asupra mediului folosind propria sa energie biologica.

O data cu evolutia omenirii si cresterii productivitatii pe plan local a dus la perfectionarea uneltelor si la necesitatea utilizarii unor energii suplimentare, aceasta energie sa gasit la animalele domestice.

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Context:Wepreviously detected a dynamic wave of gray matter loss in childhood-onset schizophrenia that started in parietal association cortices and proceeded frontally to envelop dorsolateral prefrontal and temporal cortices, including superior temporal gyri.

Objective: To map gray matter loss rates across the medial hemispheric surface, including the cingulate and medial frontal cortex, in the same cohort studied previously.
Design: Five-year longitudinal study.


Setting: National Institute of Mental Health, Bethesda, Md.

Subjects: Twelve subjects with childhood-onset schizophrenia, 12 healthy controls, and 9 medication- and IQmatched subjects with psychosis not otherwise specified.

Interventions: Three-dimensional magnetic resonance imaging at baseline and follow-up.

Main Outcome Measures: Gyral pattern and shape variations encoded by means of high-dimensional elastic deformation mappings driving each subject’s cortical anatomy onto a group average; changes in cortical gray matter mapped by computing warping fields that matched sulcal patterns across hemispheres, subjects, and time.

Results: Selective, severe frontal gray matter loss occurred bilaterally in a dorsal-to-ventral pattern across the medial hemispheric surfaces in the schizophrenic subjects.
A sharp boundary in the pattern of gray matter loss separated frontal regions and cingulate-limbic areas.

Conclusion: Frontal and limbic regions may not be equally vulnerable to gray matter attrition, which is consistent with the cognitive, metabolic, and functional vulnerability of the frontal cortices in schizophrenia. Read the rest of this entry »

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We report the dynamic anatomical sequence of human cortical gray matter development between the age of 4–21 years using quantitative four-dimensional maps and time-lapse sequences. Thirteen healthy children for whom anatomic brain MRI scans were obtained every 2 years, for 8–10 years, were studied. By using models of the cortical surface and sulcal landmarks and a statistical model for gray matter density, human cortical development could be visualized across the age range in a spatiotemporally detailed time-lapse sequence. The resulting time-lapse ‘‘movies’’ reveal that (i) higher-order association cortices mature only after lower-order somatosensory and visual cortices, the functions of which they integrate, are developed, and (ii) phylogenetically older brain areas mature earlier than newer ones. Direct comparison with normal cortical development may help understanding of some neurodevelopmental disorders such as childhood-onset schizophrenia or autism.


Human brain development is structurally and functionally a nonlinear process, and understanding normal brain maturation is essential for understanding neurodevelopmental disorders. The heteromodal nature of cognitive brain
development is evident from studies of neurocognitive performance, functional imaging (functional MRI or positronemission tomography) , and electroencephalogram coherence studies. Prior imaging studies show regional nonlinear changes in gray matter (GM) density during childhood and adolescence with prepubertal increase followed by postpubertal loss. The GM density on MRI is an indirect measure of a complex architecture of glia, vasculature, and neurons with dendritic and synaptic processes. Studies of GM maturation show a loss in corticalGMdensity over time, which temporally correlates with postmortem findings of increased synaptic pruning during adolescence and early adulthood. Here we present a study of cortical GM development in children and adolescents by using a brain-mapping technique and a prospectively studied sample of 13 healthy children (4–21 years old), who were scanned with MRI every 2 years for 8–10 years. Because the scans were obtained repeatedly on the same subjects over time, statistical extrapolation of points in between scans enabled construction of an animated time-lapse sequence (‘‘movie’’) of pediatric brain development. We hypothesized that GM development in childhood through early adulthood would be nonlinear as described before and would progress in a localized, region-specific manner coinciding with the functional maturation. We also predicted that the regions associated with more primary functions (e.g., primary motor cortex) would develop earlier compared with the regions that are involved with more complex and integrative tasks (e.g., temporal lobe).
The result is a dynamic map of GM maturation in the pre- and postpubertal period. Our results, while highlighting the remarkable heterogeneity, show that the cortical GM development appears to follow the functional maturation sequence, with the primary sensorimotor cortices along with frontal and occipital poles maturing first, and the remainder of the cortex developing in a parietal-to-frontal (back-to-front) direction. The superior temporal cortex, which contains association areas that integrate information from several sensory modalities, matured last. Furthermore, the maturation of the cortex also appeared to follow the evolutionary sequence in which these regions were created. Read the rest of this entry »

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Here we report on detailed three-dimensional maps revealing how brain structure is influenced by individual genetic differences. A genetic continuum was detected, in which brain structure was increasingly similar in subjects with increasing genetic affinity. Genetic factors significantly influenced cortical structure in Broca’s and Wernicke’s language areas, as well as frontal brain regions (r2 MZ > 0.8, p < 0.05). Preliminary correlations were performed suggesting that frontal gray matter differences may be linked to Spearman’s g, which measures successful test performance across multiple cognitive domains (p < 0.05). These genetic brain maps reveal how genes determine individual differences, and may shed light on the heritability of cognitive and linguistic skills, as well as genetic liability for diseases that affect the human cortex.


The degree to which genes and environment determine brain structure and function is of fundamental importance. Largescale neuroimaging and genetic studies are beginning to uncover normal and disease-specific patterns of gene and brain function in large human populations. Yet, little is known about the genetic control of human brain structure, and how much individual genotype accounts for the wide variations among individual brains. Recent reports show that many cognitive skills are surprisingly heritable, with strong genetic influences on IQ, verbal and spatial abilities, perceptual speed and even some personality qualities, including emotional reactions to stress. These genetic relationships persist even after statistical adjustments are made for shared family environments, which tend to make members of the same family more similar. Given that genetic and environmental factors, in utero and throughout lifetime, shape the physical development of the brain, we aimed to map patterns of brain structure that are under significant genetic control, and determine whether these structural features are linked with measurable differences in cognitive function. The few existing studies of brain structure in twins suggest that the overall volume of the brain itself and some brain structures, including the corpus callosum and ventricles, are somewhat genetically influenced, whereas gyral patterns, observed qualitatively or by comparing their twodimensional projections, are much less heritable. To make the transition from volumes of structures to detailed maps of genetic influences, advances in brain mapping technology have allowed the detailed mapping of structural features of the human cortex, including gray matter distribution, gyral patterning, and brain asymmetry. These features each vary with age, gender, handedness, hemispheric dominance and cognitive
performance in both health and disease. Composite maps of these features, generated for large populations, can reveal patterns not observable in an individual. Such patterns include statistical maps that show whether heredity and nongenetic factors are involved in determining specific aspects of brain structure.
Among the structural features that are genetically regulated and have implications for cortical function is the distribution of gray matter across the cortex. This varies widely across normal individuals, with developmental waves of gray matter gain and loss
subsiding by adulthood, and complex deficit patterns observed in Alzheimer’s disease, schizophrenia, and healthy subjects at genetic risk for these disorders. In this study, we began by comparing the average differences in gray matter (Fig. 1) in groups of unrelated subjects, dizygotic (DZ) and monozygotic (MZ) twins (see Methods). Although both types of twins share gestational and postgestational rearing environments, DZ twins share, on average, half their segregating genes, whereas MZ twins are normally genetically identical (with rare exceptions due to somatic mutations).
We found that brain structure is under significant genetic control, in a broad anatomical region that includes frontal and language-related cortices. The quantity of frontal gray matter, in particular, was most similar in individuals who were genetically alike; intriguingly, these individual differences in brain structure were tightly linked with individual differences in IQ (intelligence quotient). The resulting genetic brain maps reveal a strong relationship between genes, brain structure and behavior, suggesting
that highly heritable aspects of brain structure may be fundamental in determining individual differences in cognition. Read the rest of this entry »

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