Estudo anatômico do sistema arterial dorsal da mão

Historically, the dorsal arterial system of the hand received less attention than the palmar system. The studies concerning dorsal arterial anatomy present some controversies regarding the origin and presence of the dorsal metacarpal artery branches. Knowledge of the anatomy of dorsal metacarpal arteries is especially applied in the surgical planning for flaps taken from the dorsum of the hand. The purpose of this study is to analyze the arterial anatomy of the dorsum of the hand, compare our observations with those of previous studies from the literature, and therefore to define parameters for surgical planning for flaps supplied by the dorsal metacarpal arteries. METHOD: Twenty-six dissections were performed at the dorsum of the right hand of 26 cadavers by making a distal-based U-shaped incision. After catheterization of the radial artery at the wrist level, a plastic dye solution with low viscosity and quick solidification was injected to allow adequate exposure of even small vessels. The radial artery and its branches, the dorsal arterial arch, the dorsal metacarpal arteries, the distal and proximal communicating branches of the palmar system, and the distal cutaneous branches were carefully dissected and identified. RESULTS: The distal cutaneous branches originating from the dorsal metacarpal arteries were observed in all cases; these were located an average of 1.2 cm proximal from the metacarpophalangeal joint. The first dorsal metacarpal artery presented in 3 different patterns regarding its course: fascial, subfascial, and mixed. The branching pattern of the radial artery at the first intermetacarpal space was its division into 3 branches. We observed the presence of the dorsal arterial arch arising from the radial artery in 100% of the cases. The distance between the dorsal arterial arch and the branching point of the radial artery was an average of 2 cm. The first and second dorsal metacarpal arteries were visualized in all cases. The third and fourth dorsal metacarpal arteries were visualized in 96.2% and 92.3% of cases, respectively. There was proximal and distal communication between the dorsal arterial arch and the palmar system through the communicating branches contributing to the dorsal metacarpal artery formation. CONCLUSION: At the dorsum of the hand there is a rich arterial net that anastomoses with the palmar arterial system. This anatomical characteristic allows the utilization of the dorsal aspect of the hand as potential donor site for cutaneous flaps.Historicamente o sistema arterial dorsal da mão recebeu menos atenção em relação ao palmar. Os trabalhos que abordam a anatomia arterial dorsal apresentam pontos divergentes no que se refere a origem, a freqüência e a presença de ramos das artérias metacarpais dorsais. Este conhecimento se aplica, em especial, no planejamento cirúrgico de retalhos que tenham como área doadora o dorso da mão. O objetivo deste trabalho é o de estudar a anatomia do sistema arterial dorsal da mão, confrontando estes achados com os da literatura e desta maneira, definir parâmetros para o planejamento dos retalhos supridos pelas artérias metacarpais dorsais da mão. CASUÍSTICA E MÉTODO: Foram realizadas 26 dissecções na região dorsal da mão direita de 26 cadáveres, através de uma incisão em forma de U de base distal. Após a cateterização da artéria radial a nível do punho, foi injetado um corante plástico de baixa viscosidade e rápida solidificação que permitiu adequada visibilização até mesmo de pequenos vasos. A artéria radial e seus ramos, o arco dorsal, as artérias metacarpais dorsais, os ramos comunicantes distais e proximais do sistema palmar e os ramos cutâneos distais, foram cuidadosamente dissecados e identificados. RESULTADOS: Os ramos cutâneos distais provenientes das artérias metacarpais dorsais foram observados em todos os casos, em média, a 1,2 cm proximal a articulação metacarpo-falangeana. A primeira artéria metacarpal dorsal apresentou três padrões diferentes em relação ao seu trajeto no primeiro espaço intermetacarpal: fascial, subfascial e misto. O padrão de ramificação da artéria radial, no primeiro espaço intermetacarpal, foi o de sua divisão em três ramos. Observamos a presença do arco arterial dorsal em 100% dos casos, com sua origem na artéria radial. A distância entre a emergência do arco dorsal e o ponto de ramificação da artéria radial foi em média de 2 cm. As artérias primeira e segunda metacarpais dorsais estiveram presentes em todos os casos. As artérias terceira e quarta metacarpais dorsais estiveram presentes em 96,2% e 92,3% dos casos, respectivamente. Constatamos que houve uma comunicação proximal e distal do arco dorsal com o sistema palmar, através de ramos comunicantes que contribuíram para a formação das artérias metacarpais dorsais. CONCLUSÃO: Existe uma rica rede arterial no dorso da mão, que apresenta um grande número de anastomoses com o sistema arterial palmar, permitindo a utilização desta região como uma fonte potencial de retalhos cutâneos

Nanomorphology dependence of the environmental stability of organic solar cells

Previous studies have reported contradictory effects of small-molecule acceptors on the environmental stability of polymer:small-molecule blends, with one showing that a small-molecule acceptor stabilizes and another showing that it destabilizes the polymer donor. In this work, to investigate the origin of these contradictory results, the effects of the nanomorphologies of small-molecule acceptors on the environmental stability of polymer:small-molecule blends are demonstrated. Investigations on the environmental stabilities of polymer:fullerene blends of poly[[4, 8-bis[(2-ethylhexyl)oxy]benzo[1, 2-b:4, 5-b′]dithiophene-2, 6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3, 4-b]thiophenediyl]] (PTB7):phenyl-C₆₁-butyric acid methyl ester (PCBM) with contrasting nanomorphologies of PCBM reveal that dispersed PCBM in a mixed phase is the critical factor that causes triplet-mediated singlet oxygen generation and, hence, the severe photooxidation of PTB7, whereas an aggregated PCBM phase stabilizes PTB7 by reducing the formation of PTB7 triplet excitons. In addition, the photooxidation of PTB7 substantially degrades hole transport in the PTB7:PCBM blends by destroying the crystalline PTB7 phases within the films; this effect is strongly correlated with the efficiency losses of the PTB7:PCBM organic solar cells. These conclusions are also extended to polymer:nonfullerene blends of PTB7:ITIC and PTB7:Y6, thereby confirming the generality of this phenomenon for polymer:small-molecule organic solar cells

Elucidating Mechanisms behind Ambient Storage-Induced Efficiency Improvements in Perovskite Solar Cells

ペロブスカイト太陽電池の常温熟成機構の解明. 京都大学プレスリリース. 2021-02-17.Initial improvement in power conversion efficiency (PCE) during ambient storage is often seen in perovskite solar cells (PSCs). In this work, we studied the origin of PCE enhancement by ambient storage on typical n-i-p PSCs. We found improvements in both fill factor and open-circuit voltage during the first 2 days of storage. By analyzing temperature and light intensity-dependent VOC, we found that the charge recombination mechanism changed from surface- to bulk-dominated because of defect passivation at the perovskite surface upon storage. In addition, we found that storage improves the conductivity and lowers the highest occupied molecular orbital level of the spiro-OMeTAD, improving charge extraction. These results show that there is more than one factor causing the storage-induced improvements in perovskite solar cells

Magic Numbers and Optical Absorption Spectrum in Vertically Coupled Quantum Dots in the Fractional Quantum Hall Regime

Exact diagonalization is used to study the quantum states of vertically coupled quantum dots in strong magnetic fields. We find a new sequence of angular momentum magic numbers which are a consequence of the electron correlation in the double dot. The new sequence occurs at low angular momenta and changes into the single dot sequence at a critical angular momentum determined by the strength of the inter-dot electron tunneling. We also propose that the magic numbers can be investigated experimentally in vertically coupled dots. Because of the generalized Kohn theorem, the far-infrared optical absorption spectrum of a single dot is unaffected by correlation but the theorem does not hold for two vertically coupled dots which have different confining potentials. We show that the absorption energy of the double dot should exhibit discontinuities at the magnetic fields where the total angular momentum changes from one magic number to another.Comment: 4 pages, 3 Postscript figures, RevTeX. (to appear in Phys.Rev.B

Evolution of the Yukawa coupling constants and seesaw operators in the universal seesaw model

The general features of the evolution of the Yukawa coupling constants and seesaw operators in the universal seesaw model with det M_F=0 are investigated. Especially, it is checked whether the model causes bursts of Yukawa coupling constants, because in the model not only the magnitude of the Yukawa coupling constant (Y_L^u)_{33} in the up-quark sector but also that of (Y_L^d)_{33} in the down-quark sector is of the order of one, i.e., (Y_L^u)_{33} \sim (Y_L^d)_{33} \sim 1. The requirement that the model should be calculable perturbatively puts some constraints on the values of the intermediate mass scales and tan\beta (in the SUSY model).Comment: 21 pages, RevTex, 10 figure

A Unified Description of Quark and Lepton Mass Matrices in a Universal Seesaw Model

In the democratic universal seesaw model, the mass matrices are given by \bar{f}_L m_L F_R + \bar{F}_L m_R f_R + \bar{F}_L M_F F_R (f: quarks and leptons; F: hypothetical heavy fermions), m_L and m_R are universal for up- and down-fermions, and M_F has a structure ({\bf 1}+ b_f X) (b_f is a flavour-dependent parameter, and X is a democratic matrix). The model can successfully explain the quark masses and CKM mixing parameters in terms of the charged lepton masses by adjusting only one parameter, b_f. However, so far, the model has not been able to give the observed bimaximal mixing for the neutrino sector. In the present paper, we consider that M_F in the quark sectors are still "fully" democratic, while M_F in the lepton sectors are partially democratic. Then, the revised model can reasonably give a nearly bimaximal mixing without spoiling the previous success in the quark sectors.Comment: 7 pages, no figur

Vertically coupled double quantum dots in magnetic fields

Ground-state and excited-state properties of vertically coupled double quantum dots are studied by exact diagonalization. Magic-number total angular momenta that minimize the total energy are found to reflect a crossover between electron configurations dominated by intra-layer correlation and ones dominated by inter-layer correlation. The position of the crossover is governed by the strength of the inter-layer electron tunneling and magnetic field. The magic numbers should have an observable effect on the far infra-red optical absorption spectrum, since Kohn's theorem does not hold when the confinement potential is different for two dots. This is indeed confirmed here from a numerical calculation that includes Landau level mixing. Our results take full account of the effect of spin degrees of freedom. A key feature is that the total spin, $S$, of the system and the magic-number angular momentum are intimately linked because of strong electron correlation. Thus $S$ jumps hand in hand with the total angular momentum as the magnetic field is varied. One important consequence of this is that the spin blockade (an inhibition of single-electron tunneling) should occur in some magnetic field regions because of a spin selection rule. Owing to the flexibility arising from the presence of both intra-layer and inter-layer correlations, the spin blockade is easier to realize in double dots than in single dots.Comment: to be published in Phys. Rev. B1