Algebraic Independence and Blackbox Identity Testing

Algebraic independence is an advanced notion in commutative algebra that generalizes independence of linear polynomials to higher degree. Polynomials {f_1, ..., f_m} \subset \F[x_1, ..., x_n] are called algebraically independent if there is no non-zero polynomial F such that F(f_1, ..., f_m) = 0. The transcendence degree, trdeg{f_1, ..., f_m}, is the maximal number r of algebraically independent polynomials in the set. In this paper we design blackbox and efficient linear maps \phi that reduce the number of variables from n to r but maintain trdeg{\phi(f_i)}_i = r, assuming f_i's sparse and small r. We apply these fundamental maps to solve several cases of blackbox identity testing: (1) Given a polynomial-degree circuit C and sparse polynomials f_1, ..., f_m with trdeg r, we can test blackbox D := C(f_1, ..., f_m) for zeroness in poly(size(D))^r time. (2) Define a spsp_\delta(k,s,n) circuit C to be of the form \sum_{i=1}^k \prod_{j=1}^s f_{i,j}, where f_{i,j} are sparse n-variate polynomials of degree at most \delta. For k = 2 we give a poly(sn\delta)^{\delta^2} time blackbox identity test. (3) For a general depth-4 circuit we define a notion of rank. Assuming there is a rank bound R for minimal simple spsp_\delta(k,s,n) identities, we give a poly(snR\delta)^{Rk\delta^2} time blackbox identity test for spsp_\delta(k,s,n) circuits. This partially generalizes the state of the art of depth-3 to depth-4 circuits. The notion of trdeg works best with large or zero characteristic, but we also give versions of our results for arbitrary fields.Comment: 32 pages, preliminary versio

New molecular mediators in tumor angiogenesis

Angiogenesis is essential for tumor growth and progression. It has been demonstrated that tumor growth beyond a size 1 to 2 mm3 requires the induction of new vessels. Angiogenesis is regulated by several endogenous stimulators and inhibitors of endothelial cell migration, proliferation and tube formation. Under physiological conditions these mediators of endothelial cell growth are in balance and vessel growth is limited. In fact, within the angiogenic balance endothelial cell turnover is sufficient to maintain a functional vascular wall but does not allow vessel growth. Tumor growth an progression has successfully been correlated to the serum concentration of angiogenic mediators. Furthermore, the vascular density of tumor tissues could be correlated to the clinical course of the disease in several tumor entities. Within the last years several new mediators of endothelial cell growth have been isolated e.g. angiopoietin 1, angiopoietin 2, midkine, pleiotropin, leptin and maspin. In this review we discuss the mechanisms leading to tumor angiogenesis and describe some of the newer mediators of endothelial cell stimulation and inhibition

Comparison of Charge Deposition Profiles in Polymers Irradiated With Monoenergetic Electrons: Pulsed Electroacoustic Measurements and AF-NUMIT3 Modeling

Successful spacecraft design and charging mitigation techniques require precise and accurate knowledge of charge deposition profiles. This paper compares models of charge deposition and transport using a venerable deep dielectric charging code, AF-NUMIT3, with direct measurements of charge profiles via pulsed electroacoustic (PEA) measurements. Eight different simulations were performed for comparison to PEA experiments of samples irradiated by 50 keV or 80 keV monoenergetic electrons in vacuum and at room temperature. Two materials, polyether-ether ketone (PEEK) and polytetrafluoroethylene (PTFE), were chosen for their very low conductivities so that minimal charge migration would occur between irradiation and PEA measurements. PEEK was found to have low acoustic attenuation, while PTFE has high acoustic attenuation through the sample thicknesses of 125 μm and 250 μm for each material. The measurements were directly compared to AF-NUMIT3 simulations to validate aspects of the code and to investigate the importance of various simulation options, as well as to characterize the PEA instrumentation, measurement methods, and signal processing used. The measurement and simulation values for magnitude of charge deposition, penetration depth, and charge deposition spatial profiles are largely in agreement, though spatial and temporal distributions in incident electron flux and effects of radiation induced conductivity (RIC) and delayed RIC during the deposition process complicate the process. This work provides an experimental validation of the AF-NUMIT3 deep dielectric charging code and insight into the accuracy and precision of the PEA method

Cultural Variations and the Morphology of Innovation

The relationship between culture and innovation has intrigued researchers for generations. After much research and experimentation, what we know about the relationship is that innovation both shapes and is shaped by culture, and that both culture and innovation can be conceptualized as operating at multiple levels - national, regional, and organizational. We also know that in the management literature, culture has most commonly been conceptualized as an organizational variable - a constellation of norms and values, unique in some respects to every organization, that can, through its influence on behavior of organizational members, either encourage and facilitate innovation or be an obstacle to it

Möjliga effekter av broar och vattenfall på uttrars rörlighet i Fyrisån

Uttern (lutra lutra) klassas idag som nära hotad och antalet individer i Sverige har minskat enda sen 1950-talet. Ett av hoten mot arten är trafiken och man har sett en ökning i trafikdödligheten under flera decennier. Uttern är ett djur som äter mestadels fisk och lever därför i och nära vatten vilket gör att den ofta vandrar längs med åars stränder där infrastruktur kan bli ett hinder. Vid en bro kan uttern tvingas eller välja att gå upp på bron. Den tvingas över vägen om strömmen är för kraftig och det inte finns en torr passage eller om en bro eller trumma är översvämmad. Även vattenfall i samband med broar kan utgöra ett hinder som tvingar uttern att korsa vägbanan. Uttern kan även välja att korsa en bro via den övre vägen. Uttern spillningsmarkerar sitt revir och gör detta på till exempel stora stenar eller utstickande element på brofundamentet. Sedan slutet av 1990-talet finns det flera åtgärdsprogram och riktlinjer för att anpassa infrastruktur som utterpassage för att minska antalet viltolyckor inte bara med uttrar utan även med andra mindre däggdjur. Uppsala är en stad som har växt och växer kraftigt. Fyrisån som löper genom centrala Uppsala är ett bra exempel på en å som har påverkats kraftigt av stadsutvecklingen. Sammanlagd korsar 23 broar vattendraget under den undersökta sträckan mellan Ulva kvarn i norr och Flottsund i söder. Målet med detta arbete var att kartlägga möjliga barriäreffekter längs Fyrisån och att utvärdera hela åns funktionalitet som vandringsled för uttern. Utifrån det ska rekommendationer ges om hur sträckan kan anpassas för uttern. Under studien har ett poängsystem utvecklats för att kunna klassa broarna angående deras anpassning som utterpassage. Klassningen sträcker sig över fem klasser: utmärkt – bra – ok – risk – hinder. Studien finner att två broar kan klassas som risk och fem broar klassas som hinder. Av dessa otillräckligt anpassade broar befinner sig sex i centrala Uppsala och i samband med två vattenfall som också utgör stora hinder finns det ett stort åtgärdsbehov i Uppsala centrum. Det är framförallt murarna i centrala Uppsala som finns på båda sidor om Fyrisån som utgör ett problem och hela detta område borde anpassas av Uppsala kommun. Dock borde Kvarnfallet och Islandsfallet prioriteras eftersom dessa objekt ge upphov till de största vandringshindren. Studien ser Fyrisån som ett viktigt vattendrag i Uppsala län vilket understryker vikten av att anpassa hela sträckan för uttern. Den positiva effekten av de olika åtgärdsprogrammen och riktlinjerna ses tydligt vid Flottsundbron. Denna bro byggdes 2018 och uppfyller alla krav på en utterpassage och är därmed ett bra exempel på hur nya broar byggs för att minska risken för både människor och djur.The Eurasian otter (Lutra lutra) is near threated worldwide. In Sweden the population has decreased since the 1950s. One reason for this is the increased road mortality. As otters live by the water they often migrate along rivers where crossing infrastructures can become an obstacle. The otter can then be forced to or even choose to cross the road on the upper side. Circumstances that forces otters to do so are rapid flow or water levels higher than normal. Even waterfalls combined with bridges can become an obstacle. The reason for the otter to choose the path over the bridge lies in its behavior to mark its territory on objects that stick out, which is the case on some bridge constructions. The Swedish city of Uppsala is a fast-growing city. The Fyris-river runs through the city center and is highly affected by the town’s infrastructure. This study focuses on otters living close to Uppsala and examines the effects that the infrastructure especially bridges along the Fyris-river might have on the species. Even other parts of the infrastructure as waterfalls and walls were included. The goal of this study is to evaluate the chosen section regarding its permeability for otters and thus give an estimation on how well an otter can migrate through Uppsala. Furthermore, recommendations on how to improve the assessed bridges are giving. The section studied ranges from Ulva kvarn north of Uppsala to Flottsund in the south and includes 23 bridges as well as three waterfalls. To evaluate the bridges a score system was developed during this study summarizing several factors that are of importance if the bridge is supposed to function as an otter passage. This system is ranging over five categories: Excellent – good – okay – risk – obstacle. The study finds that two bridges can be categorized as risk and five bridges are an obstacle. Of those seven bridges, which are not functioning well as otter passage, six are in the city center of Uppsala. With two of the three waterfalls located close to those bridges, the city center is a barrier and is probably hard to migrate through for otters. There are also two bridges classified as excellent of which one, the Flottsunds-bridge, was build 2018. This bridge fulfills all requirements to function as an otter passage and is a good example for how bridges should be built since changing the policies in 2006. The study concludes that the administration of Uppsala needs to adjust several bridges, especially in Uppsala city center. The two waterfalls Kvarnfallet and Islandsfallet should be prioritized as those are the main obstacles on the assessed section

Comparison of Pulsed Electroacoustic Measurements and AF-NUMIT3 Modeling of Polymers Irradiated With Monoenergetic Electrons

Successful spacecraft design and charging mitigation techniques require precise and accurate knowledge of charge deposition profiles. This paper compares models of charge deposition and transport using a venerable deep dielectric charging code, AF-NUMIT3, with direct measurements of charge profiles via pulsed electroacoustic (PEA) measurements. Eight different simulations were performed for comparison to PEA experiments of samples irradiated by 50 or 80 keV monoenergetic electrons in vacuum and at room temperature. Two materials, polyether-ether ketone (PEEK) and polytetrafluoroethylene (PTFE), were chosen for their very low conductivities so that minimal charge migration would occur between irradiation and PEA measurements. PEEK was found to have low acoustic attenuation, while PTFE has high acoustic attenuation through the sample thicknesses of 125 and 250 μm for each material. The measurements were directly compared to AF-NUMIT3 simulations to validate aspects of the code and to investigate the importance of various simulation options, as well as to characterize the PEA instrumentation, measurement methods, and signal processing used. The measurement and simulation values for magnitude of charge deposition, penetration depth, and charge deposition spatial profiles are largely in agreement, though spatial and temporal distributions in incident electron flux and effects of radiation-induced conductivity (RIC) and delayed RIC during the deposition process complicate the process. This work provides an experimental validation of the AF-NUMIT3 deep dielectric charging code and insight into the accuracy and precision of the PEA method

The Frequency Dependence of Critical-velocity Behavior in Oscillatory Flow of Superfluid Helium-4 Through a 2-micrometer by 2-micrometer Aperture in a Thin Foil

The critical-velocity behavior of oscillatory superfluid Helium-4 flow through a 2-micrometer by 2-micrometer aperture in a 0.1-micrometer-thick foil has been studied from 0.36 K to 2.10 K at frequencies from less than 50 Hz up to above 1880 Hz. The pressure remained less than 0.5 bar. In early runs during which the frequency remained below 400 Hz, the critical velocity was a nearly-linearly decreasing function of increasing temperature throughout the region of temperature studied. In runs at the lowest frequencies, isolated 2 Pi phase slips could be observed at the onset of dissipation. In runs with frequencies higher than 400 Hz, downward curvature was observed in the decrease of critical velocity with increasing temperature. In addition, above 500 Hz an alteration in supercritical behavior was seen at the lower temperatures, involving the appearance of large energy-loss events. These irregular events typically lasted a few tens of half-cycles of oscillation and could involve hundreds of times more energy loss than would have occurred in a single complete 2 Pi phase slip at maximum flow. The temperatures at which this altered behavior was observed rose with frequency, from ~ 0.6 K and below, at 500 Hz, to ~ 1.0 K and below, at 1880 Hz.Comment: 35 pages, 13 figures, prequel to cond-mat/050203

Mycophenolate mofetil modulates adhesion receptors of the beta1 integrin family on tumor cells: impact on tumor recurrence and malignancy

BACKGROUND: Tumor development remains one of the major obstacles following organ transplantation. Immunosuppressive drugs such as cyclosporine and tacrolimus directly contribute to enhanced malignancy, whereas the influence of the novel compound mycophenolate mofetil (MMF) on tumor cell dissemination has not been explored. We therefore investigated the adhesion capacity of colon, pancreas, prostate and kidney carcinoma cell lines to endothelium, as well as their beta1 integrin expression profile before and after MMF treatment. METHODS: Tumor cell adhesion to endothelial cell monolayers was evaluated in the presence of 0.1 and 1 μM MMF and compared to unstimulated controls. beta1 integrin analysis included alpha1beta1 (CD49a), alpha2beta1 (CD49b), alpha3beta1 (CD49c), alpha4beta1 (CD49d), alpha5beta1 (CD49e), and alpha6beta1 (CD49f) receptors, and was carried out by reverse transcriptase-polymerase chain reaction, confocal microscopy and flow cytometry. RESULTS: Adhesion of the colon carcinoma cell line HT-29 was strongly reduced in the presence of 0.1 μM MMF. This effect was accompanied by down-regulation of alpha3beta1 and alpha6beta1 surface expression and of alpha3beta1 and alpha6beta1 coding mRNA. Adhesion of the prostate tumor cell line DU-145 was blocked dose-dependently by MMF. In contrast to MMF's effects on HT-29 cells, MMF dose-dependently up-regulated alpha1beta1, alpha2beta1, alpha3beta1, and alpha5beta1 on DU-145 tumor cell membranes. CONCLUSION: We conclude that MMF possesses distinct anti-tumoral properties, particularly in colon and prostate carcinoma cells. Adhesion blockage of HT-29 cells was due to the loss of alpha3beta1 and alpha6beta1 surface expression, which might contribute to a reduced invasive behaviour of this tumor entity. The enhancement of integrin beta1 subtypes observed in DU-145 cells possibly causes re-differentiation towards a low-invasive phenotype