Dimensionality and clustering in the semantic network of patients with Alzheimer's disease.

Investigated the organization of semantic memory in patients with Alzheimer's disease (AD) with a triadic comparison task. A multidimensional scaling statistic was used to analyze proximity data and to generate 3-dimensional cognitive maps that were then compared by a discriminant function analysis. Results suggest that the structure of semantic memory in AD Ss differs from that of elderly normal controls (NCs) in 2 ways. First, AD Ss are less consistent in using the attributes (predation, domesticity, and size) of concepts. Second, AD Ss focus primarily on concrete perceptual information (size), whereas NCs stress abstract conceptual knowledge (domesticity). Results are consistent with the notion that AD is characterized by a breakdown in the structure of semantic knowledge. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Dihydrobenzofuran analogues of hallucinogens. 3. Models of 4-substituted (2,5-dimethoxyphenyl)alkylamine derivatives with rigidified methoxy groups

Tetrahydrobenzodifuran functionalities were employed as conformationally restricted bioisosteres of the aromatic methoxy groups in prototypical hallucinogenic phenylalkylamines 1 and 2. Thus, a series of 8-substituted 1-(2,3,6,7-tetrahydrobenzo[1,2-b:4,5-b']difuran-4-yl)-2-aminoal kanes (7a-e) were prepared and evaluated for activity in the two-lever drug discrimination paradigm in rats trained to discriminate saline from LSD tartrate (0.08 mg/kg) and for the ability to displace [3H]ketanserin from rat cortical homogenate 5-HT2A receptors and [3H]-8-OH-DPAT from rat hippocampal homogenate 5-HT1A receptors. In addition, 1-(8-bromo-2,3,6,7-tetrahydrobenzo[1,2-b:4,5-b']difuran-4-yl)-2-am inopropane (7b), which was found to be extremely potent in the rat in vivo assays, was evaluated for its ability to compete with [125I]DOI and [3H]ketanserin binding to cells expressing cloned human 5-HT2A, 5-HT2B, and 5-HT2C receptors. All of the dihydrofuranyl compounds having a hydrophobic substituent para to the alkylamine side chain had activities in both the in vitro and in vivo assays that equaled or surpassed the activity of the analogous conformationally flexible parent compounds. For example, 7b substituted for LSD in the drug discrimination assay with an ED50 of 61 nmol/kg and had Kj values in the nanomolar to subnanomolar range for the displacement of radioligand from rat and human 5-HT2 receptors, making it one of the most potent hallucinogen-like phenylalkylamine derivatives reported to date. The results suggest that the dihydrofuran rings in these new analogues effectively model the active binding conformations of the methoxy groups of the parent compounds 1 and 2. In addition, the results provide information about the topography and relative orientation of residues involved in agonist binding in the serotonin 5-HT2 receptors.     

频谱分析的简化IF数字化

通信接收器与频谱分析仪内部信号链路的架构之间存在着相似性。利用功能强大的数字信号处理器（DSP），先进的数字接收器可在数字域中（而不像过去的产品那样在模拟域中）进行同相和正交（I-Q）信息的解调。虽然通信接收器连续执行载频和符号时钟恢复，但频谱分析仪则以“字组”的形式来捕获该信息，并以时点的方式进行存储，     

Delaying interference enhances memory consolidation in amnesic patients.

Some patients with amnesia are able to retain new information for much longer than expected when the time that follows new learning is devoid of further stimuli. Animal work shows that the absence or delaying of interference improves long-term memory consolidation. Our study suggests that this is also true for at least some patients with amnesia. Retention of new verbal material was significantly higher in a sample of patients with amnesia (N = 12) when interference occurred at the end of a 9-min delay interval than when it occurred in the middle or at the beginning of the interval. Such findings cannot be accounted for by the mere use of explicit short-term memory rehearsal. Any such rehearsal should have been blocked by the interference, irrespective of interference onset, thus leading to poor retention in all three conditions. The current findings suggest that at least some of the severe forgetting observed in amnesia is the product of a disruption of memory consolidation by immediate postlearning interference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanical properties of blends of nylon with chemically modified ABS

Tensile, flexural and impact properties were measured of a heterogeneous polymer blend system, consisting of nylon 6 and a chemically modified ABS (MABS). It was found from the tensile tests that nylon-richer blends show yielding behaviour and nylon-leaner blends show necking behaviour. The addition of MABS increases the modulus, whereas the tensile strength and percentage elongation at break decrease and go through a minimum. The impact strength is increased to a maximum of approximately three times when 20 wt% of MABS is added to nylon 6. In order to interpolate the mechanical properties observed, empirical equations are given which are found to describe the experimental data rather well. Photomicrographs were taken of the tensile fractured surfaces using a scanning electron microscope.     

Cuticular Hydrocarbons of Termites of the British Virgin Islands

A survey of the termites (Isoptera) of 17 islands of the British Virgin Island (BVI) complex yielded eight taxa belonging to three families. The Kalotermitidae include Neotermes mona (Banks), Cryptotermes brevis (Walker), Procryptotermes corniceps (Snyder), and an undetermined species of Incisitermes, likely Incisitermes nr snyderi (Light) or I. incisus (Silvestri). The only rhinotermitid collected is an undetermined species of Heterotermes (Froggatt). Parvitermes wolcotti (Snyder), Nasutitermes costalis (Holmgren), and N. acajutlae (Holmgren) comprise the Termitidae. Cuticular hydrocarbon mixtures were characterized for each of the taxa. Blends of abundant hydrocarbons are species-specific and can be used to identify a given taxon without the diagnostic castes, soldiers, or imagoes, although the species of Incisitermes were not separable on the basis of cuticular hydrocarbons.     

Prism adaptation in Alzheimer's and Huntington's disease.

13 Ss with Alzheimer's disease (AD), 14 with Huntington's disease (HD), and 16 normal elderly control Ss were compared on a perceptual adaptation task involving laterally displaced vision. All Ss were required to point to a target while wearing distorting prisms that shifted objects 20° to the right or left. Quantitative indices of baseline, preadaptation, adaptation, and aftereffects were obtained. Only HD patients failed to adapt to the prisms after visuomotor feedback and to evidence negative aftereffects when the prisms were removed. Adaptation was significantly correlated with dementia for HD patients (r?=?–.63, p?r?=?–.13, p?