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1.
Angew Chem Int Ed Engl ; 59(17): 6800-6805, 2020 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-31917887

RESUMO

Polymeric 1 ∞ [Bi]- in KBi⋅NH3 has planar zigzag chains with two-connected Bi atoms and metallic properties, whereas KBi, which has helical chains of Bi atoms, is semiconducting. The isomerization of the Bi chain is induced by solvate molecules. In the novel layered solvate structure uncharged 2 ∞ [KBi] layers are separated by intercalated NH3 molecules. These layers are a structural excerpt of the iso(valence)electronic CaSi, whose metallic properties arise from the planarity of the zigzag chain of Si atoms. Computational studies support this view, they show an anisotropic metallic behavior along the Bi chain. Electron delocalization is also found in the new cyclic anion [Bi6 ]4- isolated in K2 [K(18-crown-6)]2 [Bi6 ]⋅9 NH3 . Although [Bi6 ]4- should exhibit one localized double bond, electron delocalization is observed in analogy to the lighter homologues [P6 ]4- and [As6 ]4- . Both compounds were characterized by single-crystal X-ray structure determination.

2.
Chem Commun (Camb) ; 55(81): 12156-12159, 2019 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-31552931

RESUMO

Homoatomic cluster aggregation is a versatile route to build up atom-precise nano structures. In this work we describe the first connection of four Ge9 clusters to a single atom: in K6[Zn{η1-Ge9(Hyp)2}4]·10.5 Tol four bis-silylated Ge9 clusters are linked via one central Zn atom. Furthermore we report on the bare Ge9 cluster in (NH3)3Zn-Ge9-Zn(NH3)3·11NH3, which reveals two possible connectivity sites due to the NH3 leaving groups at the Zn atoms. Both complexes can be regarded as analogue building motifs for hypothetical tetrel element structures anticipated before with Zn atoms taking the role of four-connected tetrel atoms.

3.
Angew Chem Int Ed Engl ; 57(44): 14372-14393, 2018 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-30098108

RESUMO

Atom-precise, ligand-stabilized metalloid clusters have emerged as outstanding model systems to study fundamental structure and bonding situations of compositionally related molecules and extended solid phases. However, this fascinating field of research is still largely restricted to homometallic and pseudo-heterometallic systems of closely related d-block metals. In this review, we will highlight our own and others' efforts to project the structural and compositional diversity of intermetallics with dissimilar d- and p-block metal combinations, particularly the Zintl and Hume-Rothery phases, onto the molecular level in order to bridge the still gaping chasm between heterometallic molecular coordination chemistry and solid-state intermetallics. Herein, fundamental synthetic approaches, as well as structural and electronic properties of thus accessible "molecular alloys" will be addressed, and placed against their exceptional position as intermediates on the way to nanomaterials.

4.
J Phys Condens Matter ; 30(5): 054001, 2018 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-29303119

RESUMO

The photoinduced dynamics of two DTE-BODIPY conjugates A, B with carboxylic acid anchoring groups coupled to the surface of TiO2 were studied by ultrafast transient absorption spectroscopy. For compound A, with an orthogonal orientation of the BODIPY chromophore and the photoswitchable DTE unit, a charge separated state could not be reliably detected. Nevertheless, besides the energy transfer from the BODIPY to the ring-closed DTE-c, indications for an electron transfer reaction were found by analyzing fluorescence quenching on TiO2 in steady state fluorescence measurements. For compound B with a parallel orientation of chromophore and photoswitch, a charge separated state was conclusively identified for the coupled dyad (TiO2) via the observation of a positive absorption signal (at λ pr > 610 nm) at later delay times. An electron transfer rate of 7 × 1010 s-1 can be extracted, indicating slower processes in the dyads in comparison to previously published electron transfer reactions of DTE compounds coupled to TiO2.

5.
Angew Chem Int Ed Engl ; 56(47): 15159-15163, 2017 11 20.
Artigo em Inglês | MEDLINE | ID: mdl-28940810

RESUMO

The new [SnBi3 ]5- polyanion is obtained by the reaction of K3 Bi2 with K4 Sn9 or K12 Sn17 in liquid ammonia. The anion is iso(valence)electronic with and structurally analogous to the carbonate ion. Despite the high negative charge of the anion, the Sn-Bi bond lengths range between single and double bonds. Quantum-chemical calculations at a DFT-PBE0/def2-TZVPP/COSMO level of theory reveal that the partial double bond character between the heavy main-group atoms Bi and Sn originates from a delocalized π-electronic system. The structure of the anion is determined by single-crystal X-ray diffraction analyses of the compounds K5 [SnBi3 ] 9 NH3 (1) and K9 [K(18-crown-6)][SnBi3 ]2 ⋅15 NH3 (2). The [SnBi3 ]5- unit is the first example of a carbonate-like anion obtained from solution, and it consists exclusively of metal atoms and completes the series of metal analogues of CO and CO2 .

6.
Behav Brain Res ; 329: 58-66, 2017 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-28442359

RESUMO

OBJECTIVE: The present study aimed at revealing neurophysiological effects induced by electromyography (EMG) based biofeedback, considered as a semi-active control condition in neurofeedback studies, in adult attention-deficit/hyperactivity disorder (ADHD) patients. METHODS: 20 adult ADHD patients trained their muscle activity in the left and right supraspinatus muscle over the course of 30 EMG biofeedback sessions. Changes induced by the EMG feedback were evaluated at a clinical and neurophysiological level; additionally, the relation between changes in EEG activity recorded at the vertex over the training course and changes of symptom severity over the treatment course were assessed in order to investigate the mechanisms underlying clinical effects of EMG biofeedback. RESULTS: Participants showed significant behavioral improvements on a self-rating scale. There was a significant increase in alpha power, but no significant changes in the delta frequency range; changes in the theta and beta frequency range were not significant after adjustment for multiple comparisons. No statistically significant correlation was found between changes in EEG frequency bands and changes in ADHD symptoms. CONCLUSIONS: The current results assessed by means of a single-electrode EEG constitute a starting point regarding a clearer understanding of mechanisms underlying clinical effects of EMG biofeedback. Although we did not reveal systematic effects induced by EMG feedback on brain activity it remains an open question whether EMG biofeedback induces changes in brain regions or parameters we did not gather in the present study (e.g. motor cortex).


Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/fisiopatologia , Transtorno do Deficit de Atenção com Hiperatividade/reabilitação , Eletromiografia , Potencial Evocado Motor/fisiologia , Neurorretroalimentação/métodos , Adolescente , Adulto , Análise de Variância , Eletroencefalografia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Escalas de Graduação Psiquiátrica , Transferência de Experiência , Adulto Jovem
7.
Angew Chem Int Ed Engl ; 56(9): 2350-2355, 2017 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-28128494

RESUMO

Reactions of ZnI2 L2 (where L=[HC(PPh2 NPh)]- ) with solutions of the Zintl phase K4 Ge9 in liquid ammonia lead to retention of the Zn-Zn bond and formation of the anion [(η4 -Ge9 )Zn-Zn(η4 -Ge9 )]6- , representing the first complex with a Zn-Zn unit carrying two cluster entities. The trimeric anion [(η4 -Ge9 )Zn{µ2 (η1 :η1 Ge9 )}Zn(η4 -Ge9 )]8- forms as a side product, indicating that oxidation reactions also take place. The reaction of Zn2 Cp*2 (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) with K4 Ge9 in ethylenediamine yielded the linear polymeric unit 1∞ {[Zn[µ2 (η4 :η1 Ge9 )]}2- with the first head-to-tail arrangement of ten-atom closo-clusters. All anions were obtained and structurally characterized as [A(2.2.2-crypt)]+ salts (A=K, Rb). Copious computational analyses at a DFT-PBE0/def2-TZVPP/PCM level of theory confirm the experimental structures and support the stability of the two hypothetical ten vertex cluster fragments closo-[Ge9 Zn]2- and (paramagnetic) [Ge9 Zn]3- .

8.
Chemistry ; 22(52): 18794-18800, 2016 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-27862434

RESUMO

We report on the synthesis of new derivatives of silylated clusters of the type [Ge9 (SiR3 )3 ]- (R = SiMe3 , Me = CH3 ; R = Ph, Ph = C6 H5 ) as well as on their reactivity towards copper and zinc compounds. The silylated cluster compounds were synthesized by heterogeneous reactions starting from the Zintl phase K4 Ge9 . Reaction of K[Ge9 {Si(SiMe3 )3 }3 ] with ZnCl2 leads to the already known dimeric compound [Zn(Ge9 {Si(SiMe3 )3 }3 )2 ] (1), whereas upon the reaction with [ZnCp*2 ] the coordination of [ZnCp*]+ to the cluster takes place (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) under the formation of [ZnCp*(Ge9 {Si(SiMe3 )3 }3 )] (2). A similar reaction leads to [CuPiPr3 (Ge9 {Si(SiMe3 )3 }3 )] (3) from [CuPiPr3 Cl] (iPr=isopropyl). Further we investigated the novel silylated cluster units [Ge9 (SiPh3 )3 ]- (4) and [Ge9 (SiPh3 )2 ]- (5), which could be identified by mass spectroscopy. Bis- and tris-silylated species can be synthesized by the respective stoichiometric reactions, and the products were characterized by ESI-MS and NMR experiments. These clusters show rather different reactivity. The reaction of the tris-silylated anion 4 with [CuPiPr3 Cl] leads to [(CuPiPr3 )3 Ge9 (SiPh3 )2 ]+ as shown from NMR experiments and to [(CuPiPr3 )4 {Ge9 (SiPh3 )2 }2 ] (6), which was characterized by single-crystal X-ray diffraction. Compound 6 shows a new type of coordination of the Cu atoms to the silylated Zintl clusters.

9.
Chemistry ; 22(39): 13946-13952, 2016 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-27535342

RESUMO

The addition of Sn and Zn ions to [Ge9 ] clusters by reaction of [Ge9 ]4- with SnPh2 Cl2 , ZnCp*2 (Cp*=pentamethylcyclopentadienyl), or Zn2 [HC(Ph2 P=NPh)2 ]2 is reported. The resulting Sn- and Zn-bridged clusters [(Ge9 )M(Ge9 )]q- (M=Sn, q=4; M=Zn, q=6) display various coordination modes. The M atoms that coordinate to the open square of a C4v -symmetric [Ge9 ] cluster form strong covalent multicenter M-Ge bonds, in contrast to the M atoms coordinating to triangular cluster faces. Molecular orbital analyses show that the M atoms of the Ge9 M fragments coordinate to a second [Ge9 ] cluster with similar orbitals but in different ways. The [Ge9 Sn]2- unit donates two electrons to the triangular face of a second [Ge9 ]2- cluster with D3h symmetry, whereas [Ge9 Zn]2- acts as an electron acceptor when interacting with the triangular face of a D3h -symmetric [Ge9 ]4- unit.

10.
Clin EEG Neurosci ; 47(3): 171-9, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25802473

RESUMO

In children and adults with attention deficit/hyperactivity disorder (ADHD), a general slowing of spontaneous electroencephalographic (EEG) brain activity and a decrease of event-related potential amplitudes such as the contingent negative variation (CNV) are observed. Additionally, some studies have reported decreased skin conductance level (SCL) in this clinical population leading to the hypothesis of a peripheral hypoarousal, which may be a target of biofeedback treatment in addition to or instead of neurofeedback. To our knowledge, the relationship between SCL and CNV has not been simultaneously investigated in one experiment. Using the theoretical background of the hypoarousal model, this article aims to gain more insight into the differences and correlations of cortical (CNV) and peripheral (SCL) arousal in adults with ADHD. A sample of 23 adults with ADHD and 22 healthy controls underwent an auditory Go-NoGo task with simultaneous 22-channel EEG and SCL recordings. Reaction time (RT) and reaction time variability (RTV) were also measured to assess task performance. Significantly decreased CNV amplitude and significantly higher RTV were observed in the ADHD group, reflecting cortical underarousal and problems with sustained attention. No significant correlation between peripheral underarousal and cortical underarousal was observed in the ADHD group or the control group. The observed cortical underarousal reflected in the decreased CNV supports the notion of a reduced CNV amplitude as a possible biomarker for ADHD. However, the connection between cortical and peripheral arousal is not as clear as is suggested in previous research investigating both separately. Implications of these results for new treatment options for ADHD such as biofeedback are discussed.


Assuntos
Nível de Alerta , Transtorno do Deficit de Atenção com Hiperatividade/fisiopatologia , Atenção , Encéfalo/fisiopatologia , Resposta Galvânica da Pele , Tempo de Reação , Adulto , Eletroencefalografia/métodos , Feminino , Humanos , Masculino , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
11.
Clin Neurophysiol ; 127(2): 1374-1386, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26684900

RESUMO

OBJECTIVE: Attention Deficit-/Hyperactivity Disorder (ADHD) has been treated successfully in children with neurofeedback (NF). In this study, for the first time NF is investigated in adults with ADHD. To answer the question of specificity the relationship between treatment outcome and self-regulation ability is assessed. METHODS: Twenty-four participants underwent 30 sessions of slow cortical potential NF. Measurements of ADHD and comorbid symptoms, as well as neurophysiological data (reaction time (RT) and RT variability (RTV) and contingent negative variation (CNV)) were performed before and after treatment, and again six months after sessions were completed. Participants were categorized into self-regulation learners and non-learners. RESULTS: Significant improvements on all symptom scales were observed with medium to large effect sizes after treatment and six months post treatment. RT and RTV decreased significantly and there was a trend for an increased CNV. Half of the participants successfully learned to regulate their brain activity. In the long-term, symptoms in the group of learners improved more than in non-learners with large effect sizes. CONCLUSION: NF is effective in treating adult ADHD long-term. The impact of self-regulation ability and possible unspecific effects still require further investigation. SIGNIFICANCE: This study is the first to investigate the effects of NF in adults with ADHD, relating clinical outcome to self-regulation performance.


Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/terapia , Córtex Cerebral/fisiologia , Eletroencefalografia/métodos , Neurorretroalimentação/métodos , Neurorretroalimentação/fisiologia , Tempo de Reação/fisiologia , Adulto , Transtorno do Deficit de Atenção com Hiperatividade/diagnóstico , Transtorno do Deficit de Atenção com Hiperatividade/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estimulação Luminosa/métodos , Resultado do Tratamento , Adulto Jovem
12.
ChemMedChem ; 11(4): 420-8, 2016 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-26662886

RESUMO

Vacuolar-type H(+) -ATPases (V-ATPases) have gained recent attention as highly promising anticancer drug targets, and therefore detailed structural analyses and studies of inhibitor interactions are very important research objectives. Spin labeling of the V-ATPase holoenzyme from the tobacco hornworm Manduca sexta and V-ATPase in isolated yeast (Saccharomyces cerevisiae) vacuoles was accomplished by two novel methods involving the covalent binding of a (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) derivative of N,N'-dicyclohexylcarbodiimide (DCC) to the essential glutamate residue in the active site and the noncovalent interaction of a radical analogue of the highly potent inhibitor archazolid, a natural product from myxobacteria. Both complexes were evaluated in detail by electron paramagnetic resonance (EPR) spectroscopic studies and double electron-electron resonance (DEER) measurements, revealing insight into the inhibitor binding mode, dynamics, and stoichiometry as well as into the structure of the central functional subunit c of these medicinally important hetero-multimeric proton-translocating proteins. This study also demonstrates the usefulness of natural product derived spin labels as tools in medicinal chemistry.


Assuntos
Dicicloexilcarbodi-Imida/farmacologia , Espectroscopia de Ressonância de Spin Eletrônica , Inibidores Enzimáticos/farmacologia , Macrolídeos/farmacologia , Manduca/enzimologia , Tiazóis/farmacologia , ATPases Vacuolares Próton-Translocadoras/antagonistas & inibidores , ATPases Vacuolares Próton-Translocadoras/metabolismo , Animais , Sítios de Ligação , Óxidos N-Cíclicos/química , Dicicloexilcarbodi-Imida/química , Inibidores Enzimáticos/química , Macrolídeos/química , Manduca/efeitos dos fármacos , Modelos Moleculares , Marcadores de Spin , Tiazóis/química , ATPases Vacuolares Próton-Translocadoras/química
13.
Trials ; 16: 174, 2015 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-25928870

RESUMO

BACKGROUND: Neurofeedback has been applied effectively in various areas, especially in the treatment of children with attention-deficit/hyperactivity disorder (ADHD). This study protocol is designed to investigate the effect of slow cortical potential (SCP) feedback and a new form of neurofeedback using near-infrared spectroscopy (NIRS) on symptomatology and neurophysiological parameters in an adult ADHD population. A comparison of SCP and NIRS feedback therapy methods has not been previously conducted and may yield valuable findings about alternative treatments for adult ADHD. METHODS/DESIGN: The outcome of both neurofeedback techniques will be assessed over 30 treatment sessions and after a 6-month follow-up period, and then will be compared to a nonspecific biofeedback treatment. Furthermore, to investigate if treatment effects in this proof-of-principle study can be predicted by specific neurophysiological baseline parameters, regression models will be applied. Finally, a comparison with healthy controls will be conducted to evaluate deviant pretraining neurophysiological parameters, stability of assessment measures, and treatment outcome. DISCUSSION: To date, an investigation and comparison of SCP and NIRS feedback training to an active control has not been conducted; therefore, we hope to gain valuable insights in effects and differences of these types of treatment for ADHD in adults. TRIAL REGISTRATION: This study is registered with the German Registry of Clinical Trials: DRKS00006767 , date of registration: 8 October 2014.


Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/terapia , Córtex Cerebral/fisiopatologia , Eletromiografia , Neurorretroalimentação/métodos , Espectroscopia de Luz Próxima ao Infravermelho , Potenciais de Ação , Adulto , Transtorno do Deficit de Atenção com Hiperatividade/diagnóstico , Transtorno do Deficit de Atenção com Hiperatividade/fisiopatologia , Transtorno do Deficit de Atenção com Hiperatividade/psicologia , Protocolos Clínicos , Alemanha , Humanos , Projetos de Pesquisa , Fatores de Tempo , Resultado do Tratamento
14.
J Atten Disord ; 17(5): 393-409, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23264371

RESUMO

OBJECTIVE: The intent of this manuscript was to review all published studies on slow cortical potentials (SCP) neurofeedback for the treatment of ADHD, with emphasis on neurophysiological rationale, study design, protocol, outcomes, and limitations. METHOD: For review, PubMed, MEDLINE, ERIC, and Google Scholar searches identified six studies and six subsequent publications. In addition to five studies focusing on children with Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV)-diagnosed ADHD, one study reports on adults. RESULTS: SCP protocols utilize unipolar-electrode placement at Cz, randomized bidirectional signal regulation, feedback/transfer trials, and discrete feedback/rewards. Results demonstrated learning of SCP self-regulation, moderate to large within group effect sizes for core ADHD symptom reduction, and enhancement of event-related potentials/electroencephalogram components. Neurophysiological and session variables were predictive of treatment outcome, but open questions of specific and nonspecific effects remain. Study limitations and future directions are discussed. CONCLUSION: SCP is an efficacious and standardized neurofeedback protocol that addresses behavioral and neurophysiological deficits in ADHD.


Assuntos
Transtorno do Deficit de Atenção com Hiperatividade/fisiopatologia , Transtorno do Deficit de Atenção com Hiperatividade/terapia , Ritmo beta , Córtex Cerebral/fisiopatologia , Neurorretroalimentação/fisiologia , Ritmo Teta , Adulto , Transtorno do Deficit de Atenção com Hiperatividade/diagnóstico , Criança , Percepção de Cores , Variação Contingente Negativa , Sinais (Psicologia) , Eletroencefalografia , Potenciais Evocados/fisiologia , Retroalimentação , Humanos , Córtex Motor/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Prática Psicológica , Córtex Somatossensorial/fisiopatologia , Transferência de Experiência , Resultado do Tratamento
15.
J Proteome Res ; 11(2): 736-50, 2012 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-22098337

RESUMO

The Gram-positive bacterium Clavibacter michiganensis subsp. michiganensis (Cmm) causes wilt and canker disease of tomato (Solanum lycopersicum). Mechanisms of Cmm pathogenicity and tomato response to Cmm infection are not well understood. To explore the interaction between Cmm and tomato, multidimensional protein identification technology (MudPIT) and tandem mass spectrometry were used to analyze in vitro and in planta generated samples. The results show that during infection Cmm senses the plant environment, transmits signals, induces, and then secretes multiple hydrolytic enzymes, including serine proteases of the Pat-1, Ppa, and Sbt familes, the CelA, XysA, and NagA glycosyl hydrolases, and other cell wall-degrading enzymes. Tomato induction of pathogenesis-related (PR) proteins, LOX1, and other defense-related proteins during infection indicates that the plant senses the invading bacterium and mounts a basal defense response, although partial with some suppressed components including class III peroxidases and a secreted serine peptidase. The tomato ethylene-synthesizing enzyme ACC-oxidase was induced during infection with the wild-type Cmm but not during infection with an endophytic Cmm strain, identifying Cmm-triggered host synthesis of ethylene as an important factor in disease symptom development. The proteomic data were also used to improve Cmm genome annotation, and thousands of Cmm gene models were confirmed or expanded.


Assuntos
Actinomycetales/patogenicidade , Proteínas de Bactérias/análise , Doenças das Plantas/microbiologia , Proteínas de Plantas/análise , Proteômica/métodos , Solanum lycopersicum , Actinomycetales/fisiologia , Proteínas de Bactérias/metabolismo , Etilenos/metabolismo , Interações Hospedeiro-Patógeno , Proteínas de Plantas/metabolismo , Proteoma , Transdução de Sinais , Software , Espectrometria de Massas em Tandem
17.
Biol Psychol ; 87(2): 306-10, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21419190

RESUMO

Recent findings suggest that adults suffering from attention deficit hyperactivity disorder (ADHD) display an atypical pattern of hemispheric asymmetry, assessed through the alpha band in resting-state electroencephalogram. In the context of the approach-withdrawal model of hemispheric asymmetry, this pattern has been identified as a correlate of approach-related behavior, particularly in anterior brain regions. The current study sought to replicate previous findings on alpha asymmetry in ADHD, and to specify them based on the assumption that ADHD represents a disorder of excessive approach tendencies. A group of ADHD patients (n=19) was compared to a group of healthy controls (n=19) on measures of alpha asymmetry and aggression, an approach-related trait. Observed region-specific group differences in alpha asymmetry approximated assumptions of the approach-withdrawal model. In addition ADHD subjects displayed elevated levels of a subcomponent of aggression. These results provide support for a conceptualization of ADHD as a disorder of excessive approach tendencies.


Assuntos
Ritmo alfa/fisiologia , Transtorno do Deficit de Atenção com Hiperatividade/fisiopatologia , Adulto , Agressão/psicologia , Análise de Variância , Transtorno do Deficit de Atenção com Hiperatividade/psicologia , Manual Diagnóstico e Estatístico de Transtornos Mentais , Eletroencefalografia , Feminino , Lateralidade Funcional/fisiologia , Humanos , Classificação Internacional de Doenças , Masculino , Testes Psicológicos
18.
Behav Brain Res ; 220(1): 65-73, 2011 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-21277335

RESUMO

The present study was conducted to investigate the effect of working memory (WM) load on body processing mechanisms by using event-related potentials (ERPs). It is well known that WM load modulates the P3b (amplitude decreases as WM load increases). Additionally, WM load for faces modulates earlier ERPs like the N170. The present study aimed to investigate the effect of WM load for bodies on the P3b which is associated with WM. Additionally, we explored the effect of WM load on the N170, which is thought to be associated with configural processing, and P1, which has been observed in body as well as in face processing. Effects were analyzed during the encoding and retrieval phases. WM load was modulated by presenting one to four unfamiliar bodies simultaneously for memory encoding. The present study showed that early encoding processes (reflected by the P1 and N170) might not be modulated by WM load, whereas during the retrieval phase, early processes associated with structural encoding (N170) were affected by WM load. A possible explanation of the encoding/retrieval differences might be that subjects used distinct processing strategies in both phases. Parallel encoding of the simultaneously presented bodies might play an important role during the encoding phase where one to four bodies have to be stored, whereas serial matching might be used to compare the probe with the stored pictures during the retrieval phase. Additionally, WM load modulations were observed in later processing steps, which might be associated with stimulus identification and matching processes (reflected by the early P3b) during the encoding but not during the retrieval phase. The current findings further showed for both the encoding and the retrieval phase that the late P3b amplitude decreased as WM load for body images increased indicating that the late P3b is involved in WM processes which do not appear to be category-specific.


Assuntos
Mapeamento Encefálico , Potenciais Evocados Visuais/fisiologia , Corpo Humano , Memória de Curto Prazo/fisiologia , Rememoração Mental/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Adulto , Análise de Variância , Eletroencefalografia/métodos , Feminino , Humanos , Masculino , Estimulação Luminosa/métodos , Tempo de Reação/fisiologia , Estatística como Assunto , Adulto Jovem
19.
J Org Chem ; 74(19): 7220-9, 2009 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-19739663

RESUMO

A modular total synthesis of the potent V-ATPase inhibitors archazolid A and B is reported. The convergent preparation was accomplished by late-stage diversification of joint intermediates. Key synthetic steps involve asymmetric boron-mediated aldol reactions, two consecutive Still-Gennari olefinations to set the characteristic (Z,Z)-diene system, a Brown crotyboration, and a diastereoselective aldol condensation of highly elaborate intermediates. For macrocyclization, both an HWE reaction and a Heck coupling were successfully employed to close the 24-membered macrolactone. During the synthetic campaign, a generally useful protocol for an E-selective Heck reaction of nonactivated alkenes and a method for the direct nucleophilic displacement of the Abiko-Masamune auxiliary with sterically hindered nucleophiles were developed. The expedient and flexible strategy will enable further SAR studies of the archazolids and more detailed evaluations of target-inhibitor interactions.


Assuntos
Macrolídeos/síntese química , Tiazóis/síntese química , Macrolídeos/química , Conformação Molecular , Estereoisomerismo , Tiazóis/química , ATPases Vacuolares Próton-Translocadoras/antagonistas & inibidores
20.
Neuropsychologia ; 45(5): 1122-6, 2007 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-16999981

RESUMO

Patients with right parietal damage and spatial neglect ignore the leftward features of their environment - causing them to bump into the left-side of doorways. In contrast, the normal population shows a mild attentional bias towards the left. Self-report measures show more collisions to the right in everyday settings. We sought to obtain a quantitative measure of lateralised bumping in a laboratory setting. Participants (n=276) walked through a narrow doorway and the experimenter recorded collisions. To investigate the association between bumping and paper-and-pencil tests of pseudoneglect, a line bisection task was administered. Unilateral activation of the hemispheres has been found to ameliorate the effects of spatial neglect. We investigated the effect of activation by asking participants to move their left-, right- or both-hands as they walked. In the both hands condition, which acted as a baseline, there were more right bumps than left bumps. The rightward bias was exasperated when the left hand moved, presumably because this movement activated the right hemisphere. In contrast, there were more left bumps when the right hand moved. The results demonstrate that bumping is not random and that we collide with the right side more often. Biases in bumping, however, were not related to biases in line bisection. The effect of hand-movement demonstrates that bumping is brought about by an imbalance of activation between the hemispheres.


Assuntos
Atenção/fisiologia , Lateralidade Funcional/fisiologia , Percepção Espacial/fisiologia , Campos Visuais/fisiologia , Adulto , Feminino , Humanos , Masculino , Valores de Referência
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