Penentuan Kurva Dispersi Teoritis Polariton Magnetik Permukaan dalam Bahan Magnetoelektrik

Telah ditentukan secara teoritis kurva dispersi polariton magnetik permukaan bahan magnetoelektrik uniaxial dua subkekisi BaMnF4 dalam daerah frekuensi 0-50 cm-1, dengan perambatan gelombang tegak lurus pada sumbu mudah tanpa medan luar. Relasi dispersi tersebut diperoleh melalui persamaan-persamaan Maxwell untuk medium magnetoelektrik dengan penerapan syarat batas bagi komponen medan listrik dan magnetnya. Suseptibilitas listrik, magnetik dan magnetoelektrik bahan adalah besaran-basaran yang mengatur dinamika internal sistem magnetik tersebut. Telah ditunjukkan bahwa polariton magnetik permukaan tidak merambat dalam TM (Transverse Magnetic) tapi hanya merambat dalam ragam TE (Transverse Electric) yang bersifat nonresiprokal dengan Perubahan arah vektor gelombang menyebabkan Perubahan frekuensi atau ω (q ) ≠ ω( −q ) . Ditemukan dua jenis polariton magnetik permukaan, yaitu yang memiliki frekuensi batas magnetostatik (real mode) dan yang tidak memiliki batas magnetoelektrik (virtual mode). Kedua jenis polariton tersebut tidak terpengaruh oleh efek magnetoelektrik. Sebagai tambahan ditemukan polariton limbak dalam ragam TM yang dapat terpengaruh oleh adanya interaksi magnetoelektrik dalam bentuk munculnya ragam magnon polariton dan phonon polariton pada frekuensi tertentu. Untuk menunjukkan keberadaan polariton permukaan dilakukan pula perhitungan reflektivitas ATR (attenuated total reflection) yang ternyata dapat terdeteksi pada saat jarak antara prisma dan cuplikan mencapai nilai optimum sebesar 0,2 cm. Reflektivitas ATR dari virtual mode dapat diperoleh dengan menggunakan prisma Si(dengan tetapan dielektrik ep = 11.56), sedangkan untuk real mode diperoleh dengan e lebih besar (ep > 17) yang tentu saja belum dapat dilakukan karena belum ditemukan prisma dengan nilai ep sebesar itu. Kata kunci: Polariton Magnetik, Bahan Magnetoelektri

The role of p44/42 activation in tributyltin-induced inhibition of human natural killer cells: effects of MEK inhibitors

Destruction of tumor cells is a key function of natural killer (NK) cells. Previous studies have shown that tributyltin (TBT) can significantly reduce the lytic function of the human NK cells with accompanying increases in the phosphorylation (activation) states of the mitogen activated protein kinases (MAPKs), p44/42. The current studies examine the role of p44/42 activation in the TBT-induced reduction of NK-lytic function, by using MAPK kinase (MEK) inhibitors, PD98059 and U0126. A 1 h treatment with PD98059 or U0126 or both decreased the ability of NK cells to lyse K562 tumor cells. PD98059, U0126 or a combination of both inhibitors were able to completely block TBT-induced activation of p44/42. However, when p44/42 activation was blocked by the presence of PD98059, U0126 or the combination, subsequent exposure to TBT was still able to decrease the lytic function of NK cells. These results indicate that TBT-induced activation of p44/42 occurs via the activation of its upstream activator, MEK, and not by a TBT-induced inhibition of p44/42 phosphatase activity. Additionally, as lytic function was never completely blocked by MEK inhibitors, the results indicate that activation of p44/42 pathway is not solely responsible for the activation of lytic function of freshly isolated human NK cells. Finally, the results showed that TBT-induced activation of p44/42 is not solely responsible for the loss of lytic function

Anatomical variations and distributions of obturator nerve on Ethiopian cadavers

Variations in anatomy of the obturator nerve are important to surgeons and anesthesiologists performing surgical procedures in the pelvic cavity, medial thigh and groin regions. They are also helpful for radiologists who interpret computerized imaging and anesthesiologists who perform local anesthesia. This study aimed to describe the anatomical variations and distribution of obturator nerve. The cadavers were examined bilaterally for origin to its final distribution and the variations and normal features of obturator nerve. Sixty-seven limbs sides (34 right and 33 left sides) were studied for variation in origin and distribution of obturator nerve. From which 88.1% arises from L2, L3 and L4 and; 11.9% from L3 and L4 spinal nerves. In 23.9%, 44.8% and 31.3% of specimens the bifurcation levels of obturator nerve were determined to be intrapelvic, within the obturator canal and extrapelvic, respectively. The anterior branch subdivided into two, three and four subdivisions in 9%, 65.7% and 25.4% of the specimens, respectively, while the posterior branch provided two subdivisions in 65.7% and three subdivisions in 34.3% of the specimens. Hip articular branch arose from common obturator nerve in 67.2% to provide sensory innervation to the hip joint. Accessory obturator nerve was not observed at all in this study. Key words: Variations, obturator nerv

Beekeepers' honeybee colony selection practice in Tigray, Northern Ethiopia.

Selection of colonies plays an important role for successful harvesting of desired products from honeybees. The purpose of this study was therefore to assess local knowledge and experience of beekeepers in Tigray regional state of Ethiopia with regard to colony selection and management practices during purchase and multiplication. Respondent selection was carried out based on the existing conventional agroecological zones namely Dega (highland), Kolla (lowland) and Weinadega (midland). Four woredas (districts) from Dega zone, and three from each of Kolla and Weinadega zones were sampled. A total of 185 beekeepers were interviewed to understand the criteria they were using to select colonies. Preference ranking data were indexed using linear programming. The result indicated that beekeepers were using six local selection criteria namely worker bee population, body color, comb building direction, aggressiveness, honey yield history and age of the colony ordered according to their preference rank from 1 to 6. Beekeepers understood that selection of honeybee colonies was important because productivity, management easiness and agroclimatic adaptation of colonies are different for different colonies. As a result colonies with dominant black colored bees were chosen as first priority for their merits of better honey productivity, tolerance to absconding and multiplication easiness in Weinadega and Kolla agroecologies. However, red/yellowish colored bees were preferred in Dega agroecology

Role of Protein Kinase C in TBT-Induced Inhibition of Lytic Function and MAPK Activation in Human Natural Killer Cells

Human natural killer (NK) cells are lymphocytes that destroy tumor and virally infected cells. Previous studies have shown that exposure of NK cells to tributyltin (TBT) greatly diminishes their ability to destroy tumor cells (lytic function) while activating mitogen-activated protein kinases (MAPK) (p44/42, p38, and JNK) in NK cells. The signaling pathway that regulates NK lytic function appears to include activation of protein kinase C (PKC) as well as MAPK activity. TBT-induced activation of MAPKs would trigger a portion of the NK lytic signaling pathway, which would then leave the NK cell unable to trigger this pathway in response to a subsequent encounter with a target cell. In the present study we evaluated the involvement of PKC in inhibition of NK lysis of tumor cells and activation of MAPKs caused by TBT exposure. TBT caused a 2–3-fold activation of PKC at concentrations ranging from 50 to 300 nM (16–98 ng/ml), indicating that activation of PKC occurs in response to TBT exposure. This would then leave the NK cell unable to respond to targets. Treatment with the PKC inhibitor, bisindolylmaleimide I, caused an 85% decrease in the ability of NK cells to lyse tumor cells, validating the involvement of PKC in the lytic signaling pathway. The role of PKC in the activation of MAPKs by TBT was also investigated using bisindolylmaleimide I. The results indicated that, in NK cells where PKC activation was blocked, there was no activation of the MAPK, p44/42 in response to TBT. However, TBT-induced activation of the MAPKs, p38 and JNK did not require PKC activation. These results indicate the pivotal role of PKC in the TBT-induced loss of NK lytic function including activation of p44/42 by TBT in NK cells

Struktur Elektronik Elektron Tunggal dalam Sistem Quantum Ring

Telah dilakukan studi teoritis struktur elektronik quantum ring semikonduktor elektron tunggal dalam sistem 1D dan 2D dengan dan tanpa medan magnet secara analitik. Quantum ring direpresentasikan oleh potensial pengungkung berbentuk ()()20221rrmrV−=ω. Pengungkungan elektron dalam quantum ring 1D menunjukkan spektrum energi hanya bergantung pada kuadrat bilangan quantum magnetik 2mdan dalam pengaruh medan magnet menunjukkan fenomena menarik seperti efek Aharonov-Bohm, transport arus, dan arus kontinu (persistent current). Hasil perhitungan menunjukkan bahwa transport arus dan arus kontinu periodik dalam fluks magnetik Φ dengan periode sebesar fluks quantum ehc=Φ0. Sementara itu quantum ring 2D menunjukkan bahwa pengungkungan ini dapat menghasilkan struktur atom buatan. Perhitungan quantum ring elektron tunggal menunjukkan bahwa struktur kulit atom buatan dapat digambarkan dengan set aras energi merosot yang terisi penuh oleh 2, 8, 18, 32 dan seterusnya yang dikenal sebagai ”bilangan magis” untuk atom buatan quantum ring

Anti-colorectal cancer activity of an organometallic osmium arene azopyridine complex

This first in vivo antitumour activity for an organometallic osmium arene complex, [Os(eta(6)-p-cym)(4-(2-pyridylazo)-N,N-dimethylaniline)I]PF(6), is reported. The complex delays the growth of HCT116 human colon cancer xenografts in mice, with negligible toxicity. Its activity appears to involve redox mechanisms and its potency towards A2780 ovarian and A549 lung cancer cells is increased significantly in combination with L-buthionine-sulfoximine

Activation of p44/42 in human natural killer cells decreases cell-surface protein expression: Relationship to tributyltin-induced alterations of protein expression

Tributyltin (TBT) activates the mitogen activated protein kinase (MAPK), p44/42 in human natural killer (NK) cells. TBT also reduces NK cytotoxic function and decreases the expression of several NK-cell proteins. To understand the role that p44/42 activation plays in TBT-induced loss of NK cell function, this study investigated how selective activation of p44/42 by phorbol 12-myristate 13-acetate (PMA) affects NK cells. Previously it was shown that PMA caused losses of lytic function similar to those seen with TBT exposures. This study examined activation of p44/42 in the regulation of NK-cell protein expression and how this regulation may explain the protein expression changes seen with TBT exposures. NK cells exposed to PMA were examined for levels of cell-surface proteins, granzyme mRNA, and perforin mRNA expression. The expression of CD11a, CD16, CD18, and CD56 were reduced, perforin mRNA levels were unchanged, and granzyme mRNA levels were increased. To verify that activation of p44/42 was responsible for the alterations seen in CD11a, CD16, CD18, and CD56 with PMA, NK cells were treated with the p44/42 pathway inhibitor (PD98059) prior to PMA exposures. In the presence of PD98059, PMA caused no decreases in the expression of the cell-surface proteins. Results of these studies indicate that the activation of p44/42 may lead to the loss of NK cell cytotoxic function by decreasing the expression of CD11a, CD16, CD18, and CD56. Further, activation of p44/42 appears to be at least in part responsible for the TBT-induced decreases in expression of CD16, CD18, and CD56

Photoactivatable organometallic pyridyl ruthenium(II) arene complexes

The synthesis and characterization of a family of piano-stool RuII arene complexes of the type [(η6-arene)Ru(N,N′)(L)][PF6]2, where arene is p-cymene (p-cym), hexamethylbenzene (hmb), or indane (ind), N,N′ is 2,2′-bipyrimidine (bpm), 1,10-phenanthroline (phen), 1,10-phenanthroline-5,6-dione (phendio), or 4,7-diphenyl-1,10-phenanthroline (bathophen), and L is pyridine (Py), 4-methylpyridine (4-MePy), 4-methoxypyridine (4-MeOPy), 4,4′-bipyridine (4,4′-bpy), 4-phenylpyridine (4-PhPy), 4-benzylpyridine (4-BzPy), 1,2,4-triazole (trz), 3-acetylpyridine (3-AcPy), nicotinamide (NA), or methyl nicotinate (MN), are reported, including the X-ray crystal structures of [(η6-p-cym)Ru(bpm)(4-MePy)]2+ (2), [(η6-p-cym)Ru(bpm)(4-BzPy)]2+ (6), [(η6-p-cym)Ru(bpm)(trz)]2+ (7), [(η6-p-cym)Ru(phen)(Py)]2+ (10), and [(η6-ind)Ru(bpy)(Py)]2+ (13). These complexes can selectively photodissociate the monodentate ligand (L) when excited with UVA or white light, allowing strict control of the formation of the reactive aqua species [(η6-arene)Ru(N,N′)(OH2)]2+ that otherwise would not form in the dark. The photoproducts were characterized by UV–vis absorption and 1H NMR spectroscopy. DFT and TD-DFT calculations were employed to characterize the excited states and to obtain information on the photochemistry of the complexes. All the RuII pyridine complexes follow a relatively similar photochemical L-ligand dissociation mechanism, likely to occur from a series of 3MC triplet states with dissociative character. The photochemical process proved to be much more efficient when UVA-range irradiation was used. More strikingly, light activation was used to phototrigger binding of these potential anticancer agents with discriminating preference toward 9-ethylguanine (9-EtG) over 9-ethyladenine (9-EtA). Calf thymus (CT)-DNA binding studies showed that the irradiated complexes bind to CT-DNA, whereas the nonirradiated forms bind negligibly. Studies of CT-DNA interactions in cell-free media suggest combined weak monofunctional coordinative and intercalative binding modes. The RuII arene complexes [(η6-p-cym)Ru(bpm)(Py)]2+ (1), [(η6-p-cym)Ru(bpm)(4-MeOPy)]2+ (3), [(η6-p-cym)Ru(4,4′-bpy)]2+ (4), [(η6-hmb)Ru(bpm)(Py)]2+ (8), [(η6-ind)Ru(bpm)(Py)]2+ (9), [(η6-p-cym)Ru(phen)(Py)]2+ (10), [(η6-p-cym)Ru(bathophen)(Py)]2+ (12), [(η6-p-cym)Ru(bpm)(NA)]2+ (15), and [(η6-p-cym)Ru(bpm)(MN)]2+ (16) were cytotoxic toward A2780 human ovarian cancer cell line in the absence of photoirradiation (IC50 values in the range of 9.0–60 μM)

Bipyrimidine ruthenium(II) arene complexes : structure, reactivity and cytotoxicity

The synthesis and characterization of complexes [(η6-arene)Ru(N,N′)X][PF6], where arene is para-cymene (p-cym), biphenyl (bip), ethyl benzoate (etb), hexamethylbenzene (hmb), indane (ind) or 1,2,3,4-tetrahydronaphthalene (thn), N,N′ is 2,2′-bipyrimidine (bpm) and X is Cl, Br or I, are reported, including the X-ray crystal structures of [(η6-p-cym)Ru(bpm)I][PF6], [(η6-bip)Ru(bpm)Cl][PF6], [(η6-bip)Ru(bpm)I][PF6] and [(η6-etb)Ru(bpm)Cl][PF6]. Complexes in which N,N′ is 1,10-phenanthroline (phen), 1,10-phenanthroline-5,6-dione or 4,7-diphenyl-1,10-phenanthroline (bathophen) were studied for comparison. The RuII arene complexes undergo ligand-exchange reactions in aqueous solution at 310 K; their half-lives for hydrolysis range from 14 to 715 min. Density functional theory calculations on [(η6-p-cym)Ru(bpm)Cl][PF6], [(η6-p-cym)Ru(bpm)Br][PF6], [(η6-p-cym)Ru(bpm)I][PF6], [(η6-bip)Ru(bpm)Cl][PF6], [(η6-bip)Ru(bpm)Br][PF6] and [(η6-bip)Ru(bpm)I][PF6] suggest that aquation occurs via an associative pathway and that the reaction is thermodynamically favourable when the leaving ligand is I > Br ≈ Cl. pK a* values for the aqua adducts of the complexes range from 6.9 to 7.32. A binding preference for 9-ethylguanine (9-EtG) compared with 9-ethyladenine (9-EtA) was observed for [(η6-p-cym)Ru(bpm)Cl][PF6], [(η6-hmb)Ru(bpm)Cl]+, [(η6-ind)Ru(bpm)Cl]+, [(η6-thn)Ru(bpm)Cl]+, [(η6-p-cym)Ru(phen)Cl]+ and [(η6-p-cym)Ru(bathophen)Cl]+ in aqueous solution at 310 K. The X-ray crystal structure of the guanine complex [(η6-p-cym)Ru(bpm)(9-EtG-N7)][PF6]2 shows multiple hydrogen bonding. Density functional theory calculations show that the 9-EtG adducts of all complexes are thermodynamically preferred compared with those of 9-EtA. However, the bmp complexes are inactive towards A2780 human ovarian cancer cells. Calf thymus DNA interactions for [(η6-p-cym)Ru(bpm)Cl][PF6] and [(η6-p-cym)Ru(phen)Cl][PF6] consist of weak coordinative, intercalative and monofunctional coordination. Binding to biomolecules such as glutathione may play a role in deactivating the bpm complexes