Geometry of the non-Abelian 2-index potential and twisted de Rham cohomology

It is found that the 2-index potential in nonabelian theories does not behave geometrically as a connection but that, considered as an element of the second de Rham cohomology group twisted by a flat connection, it fits well with all the properties assigned to it in various physical contexts. We also prove some results on the Euler characteristic of the twisted de Rham complex. Finally, provided that some conditions are satisfied, we propose a non-Abelian generalisation of S-duality.Comment: 11 pages, Latex; to appear in Repts. on Math. Phy

Interplay between SIN3A and STAT3 Mediates Chromatin Conformational Changes and GFAP Expression during Cellular Differentiation

BACKGROUND: Neurons and astrocytes are generated from common neural precursors, yet neurogenesis precedes astrocyte formation during embryogenesis. The mechanisms of neural development underlying suppression and de-suppression of differentiation-related genes for cell fate specifications are not well understood. METHODOLOGY/PRINCIPAL FINDINGS: By using an in vitro system in which NTera-2 cells were induced to differentiate into an astrocyte-like lineage, we revealed a novel role for Sin3A in maintaining the suppression of GFAP in NTera-2 cells. Sin3A coupled with MeCP2 bound to the GFAP promoter and their occupancies were correlated with repression of GFAP transcription. The repression by Sin3A and MeCP2 may be an essential mechanism underlying the inhibition of cell differentiation. Upon commitment toward an astrocyte-like lineage, Sin3A- MeCP2 departed from the promoter and activated STAT3 simultaneously bound to the promoter and exon 1 of GFAP; meanwhile, olig2 was exported from nuclei to the cytoplasm. This suggested that a three-dimensional or higher-order structure was provoked by STAT3 binding between the promoter and proximal coding regions. STAT3 then recruited CBP/p300 to exon 1 and targeted the promoter for histone H3K9 and H3K14 acetylation. The CBP/p300-mediated histone modification further facilitates chromatin remodeling, thereby enhancing H3K4 trimethylation and recruitment of RNA polymerase II to activate GFAP gene transcription. CONCLUSIONS/SIGNIFICANCE: These results provide evidence that exchange of repressor and activator complexes and epigenetic modifications are critical strategies for cellular differentiation and lineage-specific gene expression

Mutations and Deregulation of Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR Cascades Which Alter Therapy Response

The Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades are often activated by genetic alterations in upstream signaling molecules such as receptor tyrosine kinases (RTK). Certain components of these pathways, RAS, NF1, BRAF, MEK1, DUSP5, PP2A, PIK3CA, PIK3R1, PIK3R4, PIK3R5, IRS4, AKT, NFKB1, MTOR, PTEN, TSC1, and TSC2 may also be activated/inactivated by mutations or epigenetic silencing. Upstream mutations in one signaling pathway or even in downstream components of the same pathway can alter the sensitivity of the cells to certain small molecule inhibitors. These pathways have profound effects on proliferative, apoptotic and differentiation pathways. Dysregulation of components of these cascades can contribute to: resistance to other pathway inhibitors, chemotherapeutic drug resistance, premature aging as well as other diseases. This review will first describe these pathways and discuss how genetic mutations and epigenetic alterations can result in resistance to various inhibitors

Doctor can I buy a new kidney? I've heard it isn't forbidden: what is the role of the nephrologist when dealing with a patient who wants to buy a kidney?

Organ trafficking is officially banned in several countries and by the main Nephrology Societies. However, this practice is widespread and is allowed or tolerated in many countries, hence, in the absence of a universal law, the caregiver may be asked for advice, placing him/her in a difficult balance between legal aspects, moral principles and ethical judgments. In spite of the Istanbul declaration, which is a widely shared position statement against organ trafficking, the controversy on mercenary organ donation is still open and some experts argue against taking a negative stance. In the absence of clear evidence showing the clinical disadvantages of mercenary transplantation compared to chronic dialysis, self-determination of the patient (and, with several caveats, of the donor) may conflict with other ethical principles, first of all non-maleficence. The present paper was drawn up with the participation of the students, as part of the ethics course at our medical school. It discusses the situation in which the physician acts as a counselor for the patient in the way of a sort of “reverse” informed consent, in which the patient asks advice regarding a complex personal decision, and includes a peculiar application of the four principles (beneficence, non-maleficence, justice and autonomy) to the donor and recipient parties

戴眼鏡對人臉辨識系統之影響

本研究嘗試不全以負面假設來看待配戴眼鏡對人臉辨識的影響。吾人將以邊緣偵測圖為基礎，以邊點強度的分析來建立一套定位眼鏡的偵測系統。同時用偵測出的鏡框位置，以邊緣點的強度、密度比較的方式，定位眼睛的位置；並以前述兩套偵測演算，採擷其過程的資訊，進一步地定位鼻子與嘴巴的位置。這些演算形成一個簡易的人臉特徵定位系統，其將可處理配戴眼鏡的人臉；吾人也將進一步地經由其處理過程與結果，分析眼鏡對區域人臉辨識的影響，進而引導出非自然物件可能對人臉辨識的阻礙或輔助。 論文也將以全域比對法中的PCA與ICA演算法作一連串的實驗，剖析眼鏡對於全域辨識的影響；此外，亦用相同的方法來測試非自然物(眼鏡)、光源亮度與人臉角度對於人臉辨識阻礙的程度，以探究是否系統值得花費更大的代價，來移除眼鏡這個被一致認定的人臉辨識障礙，並得以在辨識演算法上獲得更高的效能。The objective of this thesis is to investigate the efficacy of face recognition systems when the subjects are wearing glasses. We do not presume that non-facial features such as glasses are nuisances. Instead, we will study whether the inclusion of glasses will have a positive impact on the face detection procedure and how it affects the feature extraction process. We will demonstrate how to use techniques based on local feature analysis to reduce the uncertainties in the matching result due to interferences around the eyes and nose caused by optical glasses. We have also conducted extensive experiments to analyze the effect of glasses on face recognition systems based on global matching strategy. Specifically, we perform both principal component analysis (PCA) and independent component analysis (ICA) on face databases with different percentage of subjects wearing eye glasses. It is concluded that external objects such as glasses will have a negative impact on face recognition using global analysis approaches. However, the adverse influences of illumination and pose are more conspicuous during the recognition process. Therefore, one should take caution when attempting to adapt the global matching scheme to handle the difficulties caused by glasses