bluuebunny/crossref_metadata_2025 huggingface dataset:
Gelatinolytic activity of matrix metalloproteinase‐2 and matrix metalloproteinase‐9 in rat brain after implantation of 9L rat glioma cells
Authors: Zhao J. X. , Yang L. P. , Wang Y. F. , Qin L. P. , Liu D. Q. , Bai C. X. , Nan X. , Shi S.S. , Pei X. J.
Published: April 2007

The matrix metalloproteinases (MMPs) have come to be highlighted by their close relation to the cell invasion of gliomas. The inhibitors of MMPs have undergone extensive development because of its effectiveness against tumor invasion and angiogenesis. Therefore, a suitable animal model is necessary for searching new MMPs inhibitors against gliomas. In this study, we established an experimental model by implanting 9L glioma cells stereotactically into Fisher344 (F344) rat's brain, and the expression and enzymatic activity of MMP‐2 and MMP‐9 in 9L glioma cells and in tumor tissue was determined by means of reverse transcription polymerase chain reaction (RT‐PCR), sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) zymography, in situ film zymography and immunostaining. The results of RT‐PCR showed that the mRNA level of MMP‐2 in 9L glioma cells was higher than that of MMP‐9, and the mRNA expression of MMP‐9 was increased along with the growth of malignant gliomas. SDS‐PAGE zymography revealed that the expression of MMP‐2 and MMP‐9 were significantly increased in tumor tissues, and the MMP‐9 wasn't detected in normal tissue. The positive stain of MMP‐2 and MMP‐9 was enhanced with the growth of malignant gliomas, especially for MMP‐9. The expression of active gelatinase was found in tumor tissue. In conclusion, the expression of active MMP‐2 and MMP‐9 was increased in 9L/F344 rat brain during the growth of malignant gliomas at different time intervals, which indicate that 9L/F344 animal model may be a prospective animal model to test new MMPs inhibitors.
Neurologic manifestations of ulcerative colitis
Authors: Scheid R. , Teich N.
Published: April 2007

Ulcerative colitis (UC) has traditionally been considered to be an inflammatory disease limited to the colonic mucosa. However, since it has been shown that UC is frequently accompanied by various extraintestinal disorders, there is increasing evidence that UC may also manifest in the nervous system. The following review focuses particularly on these possible manifestations of UC, both in the peripheral (PNS), and in the central nervous system (CNS). A systematic literature search according to the MEDLINE database was performed for this purpose. Although a reliable differentiation may clinically not always be possible, three major pathogenic entities can be differentiated: (i) cerebrovascular disease as a consequence of thrombosis and thromboembolism; (ii) systemic and cerebral vasculitis; (iii) probably immune mediated neuropathy and cerebral demyelination. With the exception of thromboembolism and sensorineural hearing loss, evidence for a causal relationship relies merely on single case reports or retrospective case series. Considering the CNS‐manifestations, similarities between UC‐associated disorders of the white matter and acute disseminated encephalomyelitis (ADEM) are obvious. Epileptic seizures, unspecified encephalopathies and confusional states are most likely epiphenomena that have to be regarded symptomatic rather than as own entities. A prospective study on the neurologic aspects of UC would be very welcome.
A population‐based study on awareness of stroke in Turkey
Authors: Evci E. D. , Memis S. , Ergin F. , Beser E.
Published: April 2007

Stroke is the second most common cause of mortality and a major cause of long‐term disability of adults in most countries. This study was performed to determine the level of knowledge and awareness regarding risk factors and warning signs of stroke in a selected sample. This cross‐sectional study was carried out in Aydin between November and December 2005, utilizing a study sample of 920 people registered at urban health centers. The questionnaire, prepared by the investigators, was administered by 20 trained students utilizing face‐to‐face interviews at participants’ homes. Two‐thirds of the participants knew the organ effected by stroke. The participants reported that stroke was a consequence of occlusion (28.0%) or bleeding (18.0%) in brain arteries. Paralysis/weakness of one side of the body (37.1%), speech impairment (26.8%) and numbness of one side of the body (14.2%) were reported as three major stroke warning signs. Sixty‐four percent of the participants knew at least one of these risk factors. Their primary sources of information were family and friends. Our study showed the great need for increasing awareness of risk factors and warning signs for stroke, perhaps utilizing community based education programs and the mass media.
Post‐ictal fever: a rare symptom of partial seizures
Authors: Rossetti A. O. , Tosi C. , Despland P.‐A. , Staedler C.
Published: April 2007

Although fever may induce seizures, especially in children, its occurrence following epileptic spells has been rarely described, except from generalized convulsive status epilepticus. We present two patients suffering from focal seizures accompanied by episodes of post‐ictal fever, and review similar reports in the literature of the last 40 years. Temperature changes following non‐convulsive seizures might be induced by gene upregulation occurring in the hypothalamus, the nucleus tractus solitarius, or in other brain regions, producing a local inflammatory response. Direct propagation of electrical discharges seems less consistent with the timing of development of this symptom. Heterogeneity of reported clinical features argues against the assumption of a definite localizing or lateralizing value for post‐ictal fever.
Brain serotonin transporter binding in non‐depressed patients with Parkinson's disease
Authors: Guttman M. , Boileau I. , Warsh J. , Saint‐Cyr J. A. , Ginovart N. , McCluskey T. , Houle S. , Wilson A. , Mundo E. , Rusjan P. , Meyer J. , Kish S. J.
Published: April 2007

Early post‐mortem data suggest that damage to brain serotonin neurones might play a role in some features (e.g., depression) of Parkinson's disease (PD). However, it is not known whether such damage is a typical characteristic of living patients with PD or whether the changes are regionally widespread. To address this question we measured, by positron emission tomography imaging, levels of the brain serotonin transporter (SERT), a marker for serotonin neurones, as inferred from binding of [11C]‐3‐amino‐4‐(2‐dimethylaminomethyl‐phenylsulfanyl)‐benzonitrile (DASB), a second generation SERT radioligand, in subcortical and cerebral cortical brain areas of clinically advanced non‐depressed (confirmed by structured psychiatric interview) patients with PD. SERT binding levels in PD were lower than those in controls in all examined brain areas, with the changes statistically significant in orbitofrontal cortex (−22%), caudate (−30%), putamen (−26%), and midbrain (−29%). However, only a slight non‐significant reduction (−7%) was observed in dorsolateral pre‐frontal cortex, an area implicated in major depression. Our imaging data suggests that a modest, regionally widespread loss of brain serotonergic innervation might be a common feature of advanced PD. Further investigation will be required to establish whether SERT binding is more or less decreased in those patients with PD who also have major depressive disorder.
High prevalence of restless legs syndrome in multiple sclerosis
Authors: Manconi M. , Fabbrini M. , Bonanni E. , Filippi M. , Rocca M. , Murri L. , Ferini‐Strambi L.
Published: April 2007

Despite the fact that multiple sclerosis (MS) patients often include leg restlessness as a sensory symptom, MS is not mentioned amongst symptomatic restless legs syndrome (RLS) forms. The aim of this study was to estimate RLS prevalence in a large population of MS patients, comparing clinical and MRI findings between patients with and without RLS. Each of the 156 MS patients (100 females, 56 males, mean age 40.7 ± 10.4) enrolled in a prospective study underwent a medical history interview, a neurological examination with the assessment of the Expanded Disability Status Scale (EDSS), and a structured questionnaire to verify the presence and features of RLS. Conventional brain–spinal MRIs of 99 subjects were also evaluated and compared between patients with and without RLS. Fifty‐one subjects (32.7%) (mean age 43.8 ± 12.8) met the criteria for RLS. In a few patients (8.5%), the RLS preceded clinical MS onset, whilst in the remaining cases the RLS was followed by or was simultaneous with clinical MS onset. Comparing the RLS group with the group without RLS, no significant differences were found in MS duration, gender, and referred sleep habits. The primary progressive MS course was more represented in the RLS group, which also showed a higher EDSS score. RLS is a very common finding in MS patients and should be considered amongst the symptomatic RLS forms. RLS is also associated with higher disability.
Relevant imaging findings of cerebral aspergillosis on MRI: a retrospective case‐based study in immunocompromised patients
Authors: Gabelmann A. , Klein S. , Kern W. , Krüger S. , Brambs H.‐J. , Rieber‐Brambs A. , Pauls S.
Published: April 2007

The aim of the study was to assess neuroimaging patterns of cerebral aspergillosis with magnetic resonance imaging (1.5 T). The clinical and imaging data of nine patients were reviewed. Patients were included in the study if the diagnosis of aspergillosis was confirmed by either biopsy, autopsy, aspergillus antigen determination and/or neuroradiological and clinical response to specific treatment. Four patients had single or multiple abscesses presenting as ring‐enhancing lesions on T1‐weighted images, hypointensity of the ring on T2‐weighted MR images and low to high signal intensity on diffusion‐weighted imaging. Four patients had single or multiple infarctions affecting all compartments of the brain with hyperintensities on T2‐weighted images in three of four patients, irregular parenchymal contrast enhancement in all patients and hemorrhagic transformation of the infarcted parenchyma in one patient. Diffusion‐weighted images were positive in all ischemic areas. One patient with paranasal sinusitis developed a mycotic aneurysm of the internal carotid artery. Cerebral aspergillosis presents three principal neuroimaging findings: areas consistent with infarction; ring lesions consistent with abscess formation following infarction; and dural or vascular infiltration originating from paranasal sinusitis or orbital infiltration. Recognition of these patterns in cerebral aspergillosis may lead to more timely and effective diagnosis and treatment.
Accessory phase petrogenesis in relation to major phase assemblages in pelites from the Nelson contact aureole, southern British Columbia
Authors: TOMKINS H. S. , PATTISON D. R. M.
Published: April 2007

Monazite petrogenesis in the Nelson contact aureole is the result of allanite breakdown close to, but downgrade and therefore independent of, major phase isograds involving cordierite, andalusite and staurolite. The development of garnet downgrade of the staurolite and andalusite isograds does not appear to affect the onset of the allanite‐to‐monazite reaction but does affect the textural development of monazite. In lower pressure, garnet‐absent rocks, allanite breakdown results in localized monazite growth as pseudomorphous clusters. In higher pressure, garnet‐bearing rocks, allanite breakdown produces randomly distributed, lone grains of monazite with no textural relationship to the original reaction site. Fluids liberated from hydrous phases (chlorite, muscovite) during garnet formation may have acted as a flux to distribute light rare earth elements more widely within the rock upon allanite breakdown, preventing the localized formation of monazite pseudomorphs. Despite these textural differences, both types of monazite have very similar chemistry and an indistinguishable age by electron microprobe chemical dating (157 ± 6.4 Ma). This age range is within error of isotopic ages determined by others for the Nelson Batholith. Garnet from the garnet, staurolite and andalusite zones shows euhedral Y zoning typified by a high‐Y core, low‐Y collar and moderate‐Y annulus, the latter ascribed to allanite breakdown during garnet growth in the garnet zone. The cause of the transition from high‐Y core to low‐Y collar, traditionally interpreted to be due to xenotime consumption, is unclear because of the ubiquitous presence of xenotime. Accessory phase geothermometry involving monazite, xenotime and garnet returns inconsistent results, suggesting calibration problems or a lack of equilibration between phases.
Contaminant Removal of Domestic Wastewater by Constructed Wetlands: Effects of Plant Species
Authors: Yang Qiong , Chen Zhang‐He , Zhao Jian‐Gang , Gu Bin‐He
Published: April 2007

A comparative study of the efficiency of contaminant removal between five emergent plant species and between vegetated and unvegetated wetlands was conducted in small‐scale (2.0 m × 1.0 m × 0.7 m, length × width × depth) constructed wetlands for domestic wastewater treatment in order to evaluate the decontaminated effects of different wetland plants. There was generally a significant difference in the removal of total nitrogen (TN) and total phosphorus (TP), but no significant difference in the removal of organic matter between vegetated and unvegetated wetlands. Wetlands planted with Canna indica Linn., Pennisetum purpureum Schum., and Phragmites communis Trin. had generally higher removal rates for TN and TP than wetlands planted with other species. Plant growth and fine root (root diameter 3 mm) biomass were related to removal efficiency. Fine root biomass rather than the mass of the entire root system played an important role in wastewater treatment. Removal efficiency varied with season and plant growth. Wetlands vegetated by P. purpureum significantly outperformed wetlands with other plants in May and June, whereas wetlands vegetated by P. communis and C. indica demonstrated higher removal efficiency from August to December. These findings suggest that abundance of fine roots is an important factor to consider in selecting for highly effective wetland plants. It also suggested that a plant community consisting of multiple plant species with different seasonal growth patterns and root characteristics may be able to enhance wetland performance.
Diphenyl Ether Glycoside from the Stems of Ilex litseaefolia Hu et Tang
Authors: Xiao Yan‐Hua , Zhang Ai‐Lian , Zhang Guo‐Lin
Published: April 2007

New diphenyl ether glycoside, ilexfoliaoside, was isolated from the stems of Ilex litseaefolia Hu et Tang, along with esculetin and 3,4‐dimethoxybenzylacetic acid. The structure of ilexfoliaoside was determined as 6,2′‐dihydroxy‐4, 4′‐di‐vanilloyloxymethyl‐1,1′‐diphenyl ether 2‐O‐β‐D‐glucopyranoside on the basis of chemical and spectroscopic evidence.
Effects of Acetylcholine, Cytochalasin B and Amiprophosmethyl on Phloem Transport in Radish (Raphanus sativas)
Authors: Yang Chong‐Jun , Zhai Zhi‐Xi , Guo Yu‐Hai , Gao Peng
Published: April 2007

We investigated the role of the “sieve tube‐companion cell complex” lining the tube periphery, particularly the microfilament and microtubule, in assisting the pushing of phloem sap flow. We made a simple phloem transport system with a living radish plant, in which the conducting channel was exposed for local treatment with chemicals that are effective in modulating protoplasmic movement (acetylcholine, (ACh) a neurotransmitter in animals and insects; cytochalasin B, (CB) a specific inhibitor of many cellular responses that are mediated by microfilament systems and amiprophos‐methyl, (APM) a specific inhibitor of many cellular responses that are mediated by microtubule systems). Their effects on phloem transport were estimated by two experimental devices: (i) a comparison of changes in the amount of assimilates in terms of carbohydrates and 14C‐labeled photosynthetic production that is left in the leaf blade of treated plants; and (ii) distribution patterns of 14C‐labeled leaf assimilates in the phloem transport system. The results indicate that CB and APM markedly inhibited the transfer of photosynthetic product from leaf to root via the leaf vein, while ACh enhanced the transfer of photosynthetic product in low concentrations (5.0×10‐4 mol/L) but inhibited it in higher concentrations (2.0×10‐3 mol/L) from leaf to root via the leaf vein. Autoradiograph imaging clearly reveals that ACh treatment is more effective than the control, and both CB and APM treatments effectively inhibit the passage of radioactive assimilates. All of the results support the postulation that the peripheral protoplasm in the sieve tube serves not only as a passive semi‐permeable membrane, but is also directly involved in phloem transport.
Changes in Unsaturated Levels of Fatty Acids in Thylakoid PSII Membrane Lipids During Chilling‐induced Resistance in Rice
Authors: Zhu Su‐Qin , Yu Chun‐Mei , Liu Xin‐Yan , Ji Ben‐Hua , Jiao De‐Mao
Published: April 2007

Temperature is one of the abiotic factors limiting growth and productivity of plants. In the present work, the effect of low non‐freezing temperature, as an inducer of “chilling resistance”, was studied in three cultivars of rice (Oryza sativa L.), japonica cv. 9516 (j‐9516), the two parental lines of superhigh‐yield hybrid rice between subspecies, Peiai/E32 (ji‐PE), and the traditional indica hybrid rice Shanyou 63 (i‐SY63). Leaves of chill‐treated rice showed chilling‐induced resistance, as an increase of their low‐temperature tolerance was measured using chlorophyll fluorescence measurements, revealing a change in photosystem II (PSII) efficiency. After 5 d of exposure to 11°C under low light (100 μmol m‐2 s‐1), levels of unsaturated fatty acids in PSII thylakoid membrane lipids decreased during the initial 1‐2 d, then increased slowly and reached 99.2%, 95.3% and 90.1% of the initial value (0 d) in j‐9516, ji‐PE and i‐SY63, respectively, on the fifth day. However, under medium light (600 μmol m‐2 s‐1), all cultivars experienced similar substantial photoinhibition, which approached steady state levels after a decline in levels of unsaturated fatty acids in PSII thylakoid membrane lipids to about 57.1%, 53.8% and 44.5% of the initial values (0 d) in j‐9516, ji‐PE and I‐SY63 on the fifth day. Under either chilling‐induced resistance (the former) or low temperature photoinhibition (the latter) conditions, the changes of other physiological parameters such as D1 protein contents, electron transport activities of PSII (ETA), Fv/Fm, xanthophyl cycle activities expressed by DES (deepoxide state) were consistent with that of levels of unsaturated fatty acids in PSII thylakoid membrane lipids. So there were negative correlations between saturated levels of fatty acids (16:1(3t), 16:0, 18:0), especially the 16:1(3t) fatty acid on thylakoid membrane and other physiological parameters, such as D1 protein contents, ETA and (A+Z)/(A+V+Z). A specific role of desaturation of fatty acids and the photoprotective pigments of the xanthophyl cycle, leading to an acclimation response in thylakoid membrane lipids may be involved. We conclude that chilling‐induced resistance is accelerated by the unsaturation of thylakoid membranes, and the ability of rice plants to cold‐harden can be enhanced by genetic engineering.
Integrin‐like Protein Is Involved in the Osmotic Stress‐induced Abscisic Acid Biosynthesis in Arabidopsis thaliana
Authors: Lü Bing , Chen Feng , Gong Zhong‐Hua , Xie Hong , Liang Jian‐Sheng
Published: April 2007

We studied the perception of plant cells to osmotic stress that leads to the accumulation of abscisic acid (ABA) in stressed Arabidopsis thaliana L. cells. A significant difference was found between protoplasts and cells in terms of their responses to osmotic stress and ABA biosynthesis, implying that cell wall and/or cell wall‐plasma membrane interaction are essential in identifying osmotic stress. Western blotting and immunofluorescence localization experiments, using polyclonal antibody against human integrin β1, revealed the existence of a protein similar to the integrin protein of animals in the suspension‐cultured cells located in the plasma membrane fraction. Treatment with a synthetic pentapeptide, Gly‐Arg‐Gly‐Asp‐Ser (GRGDS), which contains an RGD domain and interacts specifically with integrin protein and thus blocks the cell wall‐plasma membrane interaction, significantly inhibited osmotic stress‐induced ABA biosynthesis in cells, but not in protoplasts. These results demonstrate that cell wall and/or cell wall‐plasma membrane interaction mediated by integrin‐like proteins played important roles in osmotic stress‐induced ABA biosynthesis in Arabidopsis thaliana.
The Geographies of Social Movements
Authors: Nicholls Walter J.
Published: April 2007

This article aims to provide a review of how geographical concepts can help us better understand the development and effects of social movements. Geographers have been rather slow to analyze the specific processes and mechanisms that make it possible for people to cooperate and engage in sustained political struggles with rich and powerful adversaries. Not only has this inattention to social movements deprived the discipline of robust conceptual tools for analyzing contentious politics, it has also limited the discipline's abilities to contend with broader theoretical issues concerning collective action and agency in the political arena. Recent research into social movements has begun to fill this void. The article maintains that the most fruitful strategy for conceptualizing the geographical underpinnings of social movements would be to examine how issues of space, scale, and place affect the processes already identified in the established sociological and political science literature on social movements.
Expanding Biogeographic Horizons with Genetic Approaches
Authors: Parker Kathleen , Markwith Scott
Published: April 2007

The last decade has seen tremendous increases in the variety and cost‐efficiency of markers available to investigate genetic questions. Molecular markers have been used in a number of biogeographic studies; however, most of this work has been done by scholars in fields other than geography, despite the inherently spatial nature of questions many authors have addressed. This article calls for greater contribution by geographers to this body of work. We begin with a primer that reviews several of the most commonly used molecular markers available today. Next, we illustrate the use of those markers with biogeographic studies in two areas that have a long‐standing tradition within geography: paleoenvironmental reconstruction and human‐biota interactions. Finally, we identify areas where genetic approaches can greatly expand our biogeographic horizons, including collaborative work with geographers in other subdisciplines, as well as with scholars in other fields.
Inequality and Why It Matters
Authors: Gilbert Alan
Published: April 2007

Many think that poverty and inequality in the world are increasing. The article shows that they are both right and wrong. But far too many, even those who worry about the world's poor, do not seem to care that the rich are becoming so much richer. The wealthy are admired and are seen as role models. Apart from the question of fairness, public disinterest in inequality is worrying because inequality blocks progress for the poor. This is important because, despite some progress, there are still billions of desperately poor people in the world and poverty is no longer confined to poor countries. Neoliberalism, combined with globalisation, has generated inequality and poverty everywhere. Today, large numbers of poor people also live in the world's richest cities. Such poverty often produces social ghettos and can ferment envy and even violence. While we need not fear the apocalypse, the danger of social strife is constantly with us. Because violence is rarely in anyone's interest perhaps geographers should take inequality, at home and abroad, more seriously than they have to date.
The Coulomb static gauge
Authors: Heras José A.
Published: April 2007

The existence of gauge conditions involving second-order derivatives of potentials is not well known in classical electrodynamics. We introduce one of these gauges, the Coulomb static gauge, in which the scalar potential is given by the Coulomb static potential. We obtain an explicit expression for the associated vector potential and show how the scalar and vector potentials in this gauge yield the retarded electric and magnetic fields. We note the close relation between the proposed gauge and the temporal gauge.
Resource Letter AON-1: Atom optics, a tool for nanofabrication
Authors: Rohwedder Bernd
Published: April 2007

This Resource Letter provides a guide to the literature on atom optics. The application of atom optics to nanofabrication has been chosen as a convenient means to introduce and illustrate the various manipulation methods currently in use. Journal articles and books are cited for the following topics: history, candidate species, manipulation physics, shapes produced, computational aspects, surface physicochemistry, and applications and perspectives.
The calming effect of oil on water
Authors: Behroozi Peter , Cordray Kimberly , Griffin William , Behroozi Feredoon
Published: April 2007

The calming effect of oil on water has been known since ancient times. Benjamin Franklin was the first to investigate the effect, but the underlying mechanism for this striking phenomenon remains elusive. We used a miniature laser interferometer to measure the amplitude of surface waves to a resolution of ±5nm, making it possible to determine the effect of an oil monolayer on the attenuation of capillary waves and the surface dilational modulus of the monolayer. We present attenuation data on pure water, water covered by olive oil, water covered by a fatty acid, and a water-acetone mixture for comparison. From the attenuation data at frequencies between 251 and 551Hz, we conclude that the calming effect of oil on surface waves is principally due to the dissipation of wave energy caused by the Gibbs surface elasticity of the monolayer, with only a secondary contribution from the reduction in surface tension. Our data also indicate that the surface-dilational viscosity of the oil monolayer is negligible and plays an insignificant role in calming the waves.
Some Interesting Thermodynamics of the Thermos Flask
Authors: Berger Roland
Published: April 2007

When opening a thermos flask filled with coffee, one often “hears” the equalization of the pressure difference that appears to be present between the air cavity inside the flask and the surrounding room atmosphere. Recently we discussed this phenomenon while drinking coffee and guessed about the direction of the gas stream accompanying the pressure release. Our hypotheses were tested, and we found that the pressure was higher inside the flask. But this only holds when the coffee is fresh. After some hours one observes an inversion; the pressure inside drops clearly under the environmental value and we wondered—what is going on inside the flask? That question gives the opportunity to discuss some basic thermodynamic concepts, with different degrees of difficulty, in a motivating manner.
Torsional Oscillations with Lorentz Force
Authors: Gluck Paul
Published: April 2007

We have built a device that uses the Lorentz force on a current-carrying wire situated in a magnetic field, F = I L × B, in order to demonstrate a slowly varying alternating current by means of an optical lever. The apparatus consists of a horseshoe magnet, a length of thin enamel-coated wire (ours was 0.3 mm thick), a signal generator, a rheostat, and a laser. Construction is illustrated in the diagram (Fig. 1).
Report on the 2006 AAPT Apparatus Competition
Authors: Flarend Richard
Published: April 2007

Each year at the AAPT summer meeting there is an apparatus competition in which members of the physics community can share ideas for new or improved apparatus to aid in the teaching of physics. The 2006 competition at the summer meeting in Syracuse, NY, was the largest competition in quite a while and continued an upward trend in the number of entries. Entries ranged in complexity, cost, and target audience, from a $20 apparatus for experimenting with standing waves on the surface of water, to an open design of an atomic force microscope (Fig. 1), which was also relatively low in cost (as far as AFMs go) at around $15,000.
Magnetic Levitation and Newton's Third Law
Authors: Aguilar Horacio Munguía
Published: April 2007

Newton's third law is often misunderstood by students and even their professors, as has already been pointed out in the literature.1,2 Application of the law in the context of electromagnetism can be especially problematic, because the idea that the forces of “action” and “reaction” are equal and opposite independent of the medium through which they act can be muddied by the concept of “action at a distance.” While some experiments have been described3,4 illustrating Newton's third law in magnetic situations, these do not offer the student a clear way of evaluating his/her own preconceptions. The experiment we present shows how easily the student, and even the graduate student, can fail to apply the third law correctly in an electromagnetic situation. The experiment described here employs a magnetic levitator and shows the difficulty in recognizing action and reaction forces.
Converting Between °C and °F: A Teachable Moment
Authors: Day Lawrence
Published: April 2007

Converting between degrees Celsius and degrees Fahrenheit isn't difficult. Remembering when to multiply by 5/9 or 9/5 and whether you have to add 32 or subtract 32 makes it fairly easy. Sometimes, though, fairly easy isn't easy enough. Students have trouble remembering the order of operations: “Do I add or subtract 32, and is that before or after I multiply?” Of course, knowing that 32° Fahrenheit is 0° Celsius helps with remembering, but students don't always see it that way. And why is it that you subtract first when going from °F to °C, but multiply first when going the other way?
Thermodynamics of a Block Sliding Across a Frictional Surface
Authors: Mungan Carl E.
Published: April 2007

The following idealized problem is intended to illustrate some basic thermodynamic concepts involved in kinetic friction. A block of mass m is sliding on top of a frictional,1 flat-topped table of mass M. The table is magnetically levitated, so that it can move without thermal contact and friction across a horizontal floor. The table is initially stationary, while the block has initial speed vi and slides to rest relative to the table. The block and table are inside a large vacuum tank, so there is no air resistance, buoyancy, nor thermal losses to the atmosphere. Furthermore the inner surface of the vacuum tank is a perfect mirror so that the tank does not radiatively exchange heat with the block and table. The block and table are homogeneous, both initially have temperature Ti, and they each have large thermal conductivities so that they rapidly attain a common final temperature Tf after the block has come to rest. The specific heat capacity of the block is cb and that of the table is ct, and these heat capacities are assumed to be temperature independent over the range of temperatures that arises in this problem. (a) Find the common final speed vf and temperature Tf of the block and table. (b) Find the changes in the bulk kinetic energies K (in the center-of-mass frame of the isolated block-table system), the internal energies U, and the entropies S of the block and table. (c) Discuss the first and second laws of thermodynamics in connection with these results.
Newton's Apple
Authors: Hendry Archibald W.
Published: April 2007

Isaac Newton may have seen an apple fall, but it was Robert Hooke who had a better idea of where it would land. No one really knows whether or not Isaac Newton actually saw an apple fall in his garden. Supposedly it took place in 1666, but it was a tale he told in his old age more than 60 years later, a time when his memory was failing and his recollections of events did not always match known facts. However, one thing is certain—falling objects were to play a key part in Newton's eventual understanding of how objects move.
Have You Been to a Good Physics Fight Lately?
Authors: Oldaker Bruce
Published: April 2007

The United States Association for Young Physicists Tournaments (USAYPT) held its annual February Tournaments on Feb. 9–10, 2007, at the North Carolina School for Science and Mathematics, Durham, NC. Young physicists' tournaments are theoretical and experimental research-based team competitions described more fully at the USAYPT website: http://www.usaypt.org.
Prepare for Landing
Authors: DiLisi Gregory A. , Rarick Richard A.
Published: April 2007

The 2006 Winter Meeting of the AAPT Was Over … and the flight home from Anchorage to Cleveland was just about to end—eight hours in the air, only two complimentary beverages, no meals, a jump across four time zones, a one-year-old baby daughter, and a wife whose motto for the week was, “Why did they choose to have a winter meeting in Alaska?” made for a mentally and physically taxing airborne ordeal. As we entered the last hour of flight, my small family was exhausted and the pilot's decision to dim the interior cabin lights mixed with the soothing hum of the Airbus® A320's engines quickly put us to sleep. Fading in and out of my delirium, I eventually heard the pilot's voice crackle over the intercom with a seemingly innocent comment: “We are going to begin our final descent into Cleveland … we should have you on the ground in exactly eight minutes.” Something about the pilot's use of the word “exactly” must have triggered a reaction in my brain, because his remarks initiated a series of calculations: So how fast are we flying? How high are we flying? What's our angle of descent? With only eight minutes until touchdown, my curiosity to determine the descending airplane's motion led me to conduct a hastily constructed experiment.
Graphical Representation of the Doppler Shift: Classical and Relativistic
Authors: Rojas R. , Fuster G.
Published: April 2007

The Doppler shift is a frequency change of a repetitive effect, as measured by a receiver, due to the motion of the wave emitter, to the motion of the wave receiver, or both. A demonstration of the effect is provided by the sound of a car's horn that changes from a higher pitch to a lower pitch when a car drives past.1 Most derivations of the Doppler formula assume sinusoidal waves.2–4 We want to call the attention of readers to a derivation that uses a graphical representation based on a graph of position versus time.5 We will adopt a particle model of machine gun bullets fired at a constant period,6–8 thus getting a derivation that just requires the knowledge of kinematics. Furthermore, we will explain how to introduce the time dilation in order to get the formula for the relativistic Doppler shift.
Epidemiology and Control of Neosporosis andNeospora caninum
Authors: Dubey J. P. , Schares G. , Ortega-Mora L. M.
Published: April 2007

Neospora caninumis a protozoan parasite of animals. Until 1988, it was misidentified asToxoplasma gondii. Since its first recognition in dogs in 1984 and the description of the new genus and speciesNeospora caninumin 1988, neosporosis has emerged as a serious disease of cattle and dogs worldwide. Abortions and neonatal mortality are a major problem in livestock operations, and neosporosis is a major cause of abortion in cattle. Although antibodies toN. caninumhave been reported, the parasite has not been detected in human tissues. Thus, the zoonotic potential is uncertain. This review is focused mainly on the epidemiology and control of neosporosis in cattle, but worldwide seroprevalences ofN. caninumin animals and humans are tabulated. The role of wildlife in the life cycle ofN. caninumand strategies for the control of neosporosis in cattle are discussed.
Human Protothecosis
Authors: Lass-Flörl Cornelia , Mayr Astrid
Published: April 2007

Human protothecosis is a rare infection caused by members of the genusPrototheca. Protothecaspecies are generally considered to be achlorophyllic algae and are ubiquitous in nature. The occurrence of protothecosis can be local or disseminated and acute or chronic, with the latter being more common. Diseases have been classified as (i) cutaneous lesions, (ii) olecranon bursitis, or (iii) disseminated or systemic manifestations. Infections can occur in both immunocompetent and immunosuppressed patients, although more severe and disseminated infections tend to occur in immunocompromised individuals.Prototheca wickerhamiiandPrototheca zopfiihave been associated with human disease. Usually, treatment involves medical and surgical approaches; treatment failure is not uncommon. Antifungals such as ketoconazole, itraconazole, fluconazole, and amphotericin B are the most commonly used drugs to date. Among them, amphotericin B displays the best activity againstProtothecaspp. Diagnosis is largely made upon detection of characteristic structures observed on histopathologic examination of tissue.
Helicobacter pyloriDetection and Antimicrobial Susceptibility Testing
Authors: Mégraud Francis , Lehours Philippe
Published: April 2007

The discovery ofHelicobacter pyloriin 1982 was the starting point of a revolution concerning the concepts and management of gastroduodenal diseases. It is now well accepted that the most common stomach disease, peptic ulcer disease, is an infectious disease, and all consensus conferences agree that the causative agent,H. pylori, must be treated with antibiotics. Furthermore, the concept emerged that this bacterium could be the trigger of various malignant diseases of the stomach, and it is now a model for chronic bacterial infections causing cancer. Most of the many different techniques involved in diagnosis ofH. pyloriinfection are performed in clinical microbiology laboratories. The aim of this article is to review the current status of these methods and their application, highlighting the important progress which has been made in the past decade. Both invasive and noninvasive techniques will be reviewed.
Avian Influenza Virus (H5N1): a Threat to Human Health
Authors: Peiris J. S. Malik , de Jong Menno D. , Guan Yi
Published: April 2007

Pandemic influenza virus has its origins in avian influenza viruses. The highly pathogenic avian influenza virus subtype H5N1 is already panzootic in poultry, with attendant economic consequences. It continues to cross species barriers to infect humans and other mammals, often with fatal outcomes. Therefore, H5N1 virus has rightly received attention as a potential pandemic threat. However, it is noted that the pandemics of 1957 and 1968 did not arise from highly pathogenic influenza viruses, and the next pandemic may well arise from a low-pathogenicity virus. The rationale for particular concern about an H5N1 pandemic is not its inevitability but its potential severity. An H5N1 pandemic is an event of low probability but one of high human health impact and poses a predicament for public health. Here, we review the ecology and evolution of highly pathogenic avian influenza H5N1 viruses, assess the pandemic risk, and address aspects of human H5N1 disease in relation to its epidemiology, clinical presentation, pathogenesis, diagnosis, and management.
Induction of Apoptosis by the Severe Acute Respiratory Syndrome Coronavirus 7a Protein Is Dependent on Its Interaction with the Bcl-X
L
Protein
Authors: Tan Ying-Xim , Tan Timothy H. P. , Lee Marvin J.-R. , Tham Puay-Yoke , Gunalan Vithiagaran , Druce Julian , Birch Chris , Catton Mike , Fu Nai Yang , Yu Victor C. , Tan Yee-Joo
Published: April 2007

The severe acute respiratory syndrome coronavirus (SARS-CoV) 7a protein, which is not expressed by other known coronaviruses, can induce apoptosis in various cell lines. In this study, we show that the overexpression of Bcl-X
L
, a prosurvival member of the Bcl-2 family, blocks 7a-induced apoptosis, suggesting that the mechanism for apoptosis induction by 7a is at the level of or upstream from the Bcl-2 family. Coimmunoprecipitation experiments showed that 7a interacts with Bcl-X
L
and other prosurvival proteins (Bcl-2, Bcl-w, Mcl-1, and A1) but not with the proapoptotic proteins (Bax, Bak, Bad, and Bid). A good correlation between the abilities of 7a deletion mutants to induce apoptosis and to interact with Bcl-X
L
was observed, suggesting that 7a triggers apoptosis by interfering directly with the prosurvival function of Bcl-X
L
. Interestingly, amino acids 224 and 225 within the C-terminal transmembrane domain of Bcl-X
L
are essential for the interaction with the 7a protein, although the BH3 domain of Bcl-X
L
also contributes to this interaction. In addition, fractionation experiments showed that 7a colocalized with Bcl-X
L
at the endoplasmic reticulum as well as the mitochondria, suggesting that they may form complexes in different membranous compartments.
Successful Topical Respiratory Tract Immunization of Primates against Ebola Virus
Authors: Bukreyev Alexander , Rollin Pierre E. , Tate Mallory K. , Yang Lijuan , Zaki Sherif R. , Shieh Wun-Ju , Murphy Brian R. , Collins Peter L. , Sanchez Anthony
Published: April 2007

Ebola virus causes outbreaks of severe viral hemorrhagic fever with high mortality in humans. The virus is highly contagious and can be transmitted by contact and by the aerosol route. These features make Ebola virus a potential weapon for bioterrorism and biological warfare. Therefore, a vaccine that induces both systemic and local immune responses in the respiratory tract would be highly beneficial. We evaluated a common pediatric respiratory pathogen, human parainfluenza virus type 3 (HPIV3), as a vaccine vector against Ebola virus. HPIV3 recombinants expressing the Ebola virus (Zaire species) surface glycoprotein (GP) alone or in combination with the nucleocapsid protein NP or with the cytokine adjuvant granulocyte-macrophage colony-stimulating factor were administered by the respiratory route to rhesus monkeys—in which HPIV3 infection is mild and asymptomatic—and were evaluated for immunogenicity and protective efficacy against a highly lethal intraperitoneal challenge with Ebola virus. A single immunization with any construct expressing GP was moderately immunogenic against Ebola virus and protected 88% of the animals against severe hemorrhagic fever and death caused by Ebola virus. Two doses were highly immunogenic, and all of the animals survived challenge and were free of signs of disease and of detectable Ebola virus challenge virus. These data illustrate the feasibility of immunization via the respiratory tract against the hemorrhagic fever caused by Ebola virus. To our knowledge, this is the first study in which topical immunization through respiratory tract achieved prevention of a viral hemorrhagic fever infection in a primate model.
SCHEDULING ALGORITHMS FOR DATA REDISTRIBUTION AND LOAD-BALANCING ON MASTER-SLAVE PLATFORMS
Authors: MARCHAL LORIS , REHN VERONIKA , ROBERT YVES , VIVIEN FRÉDÉRIC
Published: April 2007

In this work we are interested in the problem of scheduling and redistributing data on master-slave platforms. We consider the case were the workers possess initial loads, some of which having to be redistributed in order to balance their completion times. We assume that the data consists of independent and identical tasks. We prove the NP completeness of the problem for fully heterogeneous platforms. Also, we present optimal polynomial algorithms for special important topologies: a simple greedy algorithm for homogeneous star-networks, and a more complicated algorithm for platforms with homogeneous communication links and heterogeneous workers.
DARK ENERGY MODELS AND SUPERNOVA RELIC NEUTRINOS
Authors: ONO HIROYUKI , SUZUKI HIDEYUKI
Published: April 2007

Recent cosmological observations show that the unknown energy element called dark energy dominates in the universe. In this letter, we investigate to what extent dark energy models influence supernova relic neutrino (SRN) spectra when the supernova rate could be determined by direct counting and discuss the possibility to distinguish dark energy models using future observation of SRN. We found that the total number of SRN events in GCG model will be larger than those in ΛCDM and holographic dark energy models by 20%. As a result, we find a possibility to distinguish GCG model from ΛCDM and holographic dark energy models using observation of SRN. SRN should be a unique probe into dark energy models and will play complementary roles to other observables.
STUDY OF THE EFFECT OF CAPILLARY PRESSURE ON PERMEABILITY
Authors: LIU YANJUN , YU BOMING , XU PENG , WU JINSUI
Published: April 2007

A fractal permeability model which accounts for the capillary pressure is derived, and the permeability contribution from the capillary pressure is analyzed. The predicted permeability is compared with the available experimental data, and good agreement is found between the present model predictions and available experimental data. The results show that at low porosity (< 0.35), the capillary pressure has the significant influence on the total permeability, and the capillary pressure effect cannot be neglected. But at high porosity (> 0.35), the effect of capillary pressure on permeability is insignificant.
STRUCTURAL SCALING IN BACH'S CELLO SUITE NO. 3
Authors: BROTHERS HARLAN J.
Published: April 2007

The Bourrée Part I from Johann Sebastian Bach's Cello Suite No. 3 provides a clear example of structural scaling. The recursive form of this structure can be visualized in the manner of a well known fractal construction — the Cantor set.
MINORITY AND MAJORITY GAMES IN FINANCIAL MARKETS
Authors: KIM KYUNGSIK , YOON SEONG-MIN , KIM SOO YONG , TAKAYASU HIDEKI
Published: April 2007

We study the game theory from tick data of the won-dollar and yen-dollar exchange rates in financial markets. The standard deviation, the global efficiency, and the autocorrelation for arbitrary strategies are shown to give rise to properties of new dynamics, and these statistical quantities are very similar with the case of the majority game. Our results presented will be compared with numerical findings for other game models.
FRACTAL ANALYSIS OF DENDRITIC ARBORISATION PATTERNS OF STALKED AND ISLET NEURONS IN SUBSTANTIA GELATINOSA OF DIFFERENT SPECIES
Authors: MILOŠEVIĆ NEBOJŠA T. , RISTANOVIĆ DUŠAN , STANKOVIĆ JOVAN B. , GUDOVIĆ RADMILA
Published: April 2007

Through analysis of the morphology of dendritic arborisation of neurons from the substantia gelatinosa of dorsal horns from four different species, we have established that two types of cells (stalked and islet) are always present. The aim of the study was to perform the intra- and/or inter-species comparison of these two neuronal populations by fractal analysis, as well as to clarify the importance of the fractal dimension as an objective and usable morphological parameter. Fractal analysis was carried out adopting the box-counting method. We have shown that the mean fractal dimensions for the stalked cells are significantly different between species. The same is true for the mean fractal dimensions of the islet cells. Still, no significant differences were found for the fractal dimensions of the stalked and islet cells within a particular species. The human species has shown as the only exception where fractal dimensions of these two types of cells differ significantly. This study shows once more that the fractal dimension is a useful and sensitive morphological descriptor of neuronal structures and differences between them.