Comparison of age-extended norms for the Wechsler Adult Intelligence Scale—Revised in patients with Alzheimer's disease.

Recent studies by R. J. Ivnik et al (see record 1993-04116-001), J. F. Malec et al (see record 1993-04120-001), and J. J. Ryan et al (see record 1991-08835-001) have provided age-extended norms for the Wechsler Adult Intelligence Scale—Revised (WAIS—R). The current study compared IQ scores based on these newer age-extended norms in 216 elderly Alzheimer's disease (AD) patients. Results showed that when the norms from Ryan et al were used, IQ scores were consistently the same as or higher than when WAIS—R manual norms were used. When the norms provided by Ivnik et al and Malec et al were used, IQ scores tended to be lower than WAIS—R manual norms for younger patients with more intellectual impairment. Results illustrate the importance of reporting the normative sample upon which IQ test scores for older adults are based and provide guidelines for selecting which set of age-extended WAIS—R norms to use with cognitively impaired elderly Ss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Low complexity affine MMSE detector for iterative detection-decoding MIMO OFDM systems

Iterative turbo processing between detection and decoding shows near-capacity performance on a multiple-antenna system. Combining iterative processing with optimum front-end detection is particularly challenging because the front-end maximum a posteriori (MAP) algorithm has a computational complexity that is exponential. Sub-optimum detector such as the soft interference cancellation linear minimum mean square error (SIC-LMMSE) detector with near front-end MAP performance has been proposed in the literature. The asymptotic computational complexity of SIC-LMMSE is O(n_t ²n_r + n_tn_r ³ + n_tM_c2^Mc) per detection-decoding cycle where n_t is number of transmit antenna, nr is number of receive antenna, and Mc is modulation size. A lower complexity detector is the hard interference cancellation LMMSE (HIC-LMMSE) detector. HIC-LMMSE has asymptotic complexity of O(n_t ²n_r + n_tM_c2^Mc) but suffers extra performance degradation. In this paper, two front-end detection algorithms are introduced that not only achieve asymptotic computational complexity of O(n_t ²n_r + n_tn_r ² [Gamma (beta) + 1] + n_tM_c2^Mc) where Gamma(beta) is a function with discrete output {-1, 2, 3, ...,n_t} and O(n_tM_c2^Mc) respectively. Simulation results demonstrate that the proposed low complexity detection algorithms offer exactly same performance as their full complexity counterpart in an iterative receiver while being computational more efficient.     

Syndrome: a light‐weight approach to improving TCP performance in mobile wireless networks

It is well known that the performance of TCP deteriorates in a mobile wireless environment. This is due to the fact that although the majority of packet losses are results of transmission errors over the wireless links, TCP senders still take packet loss as an indication of congestion, and adjust their congestion windows according to the additive increase and multiplicative decrease (AIMD) algorithm. As a result, the throughput attained by TCP connections in the wireless environment is much less than it should be. The key problem that leads to the performance degradation is that TCP senders are unable to distinguish whether packet loss is a result of congestion in the wireline network or transmission errors on the wireless links. In this paper, we propose a light‐weight approach, called syndrome, to improving TCP performance in mobile wireless environments. In syndrome, the BS simply counts, for each TCP connection, the number of packets that it relays to the destination host so far, and attaches this number in the TCP header. Based on the combination of the TCP sequence number and the BS‐attached number and a solid theoretical base, the destination host will be able to tell where (on the wireline or wireless networks) packet loss (if any) occurs, and notify TCP senders (via explicit loss notification, ELN) to take appropriate actions. If packet loss is a result of transmission errors on the wireless link, the sender does not have to reduce its congestion window. Syndrome is grounded on a rigorous, analytic foundation, does not require the base station to buffer packets or keep an enormous amount of states, and can be easily incorporated into the current protocol stack as a software patch. Through simulation studies in ns‐2 (UCB, LBNL, VINT network simulator, http://www‐mash.cs.berkeley.edu/ns/ ), we also show that syndrome significantly improves the TCP performance in wireless environments and the performance gain is comparable to the heavy‐weight SNOOP approach (either with local retransmission or with ELN) that requires the base station to buffer, in the worst case, a window worth of packets or states. Copyright © 2001 John Wiley & Sons, Ltd.     

Conical Boron Nitride Nanorods Synthesized Via the Ball-Milling and Annealing Method

A boron nitride (BN) nanostructure, conical BN nanorod, has been synthesized in a large quantity on Si substrates for the first time via the ball-milling and annealing method. Nitridation of milled boron carbide (B₄C) powders was performed in nitrogen gas at 1300°C on the surface of the substrates to form the BN nanorods. The highly crystallized nanorods consist of conical BN basal layers stacked along the nanorod axis. Ball milling of the B₄C powders can significantly enhance the nitridation of the powders and thus facilitate the formation of nanorods during the annealing process.     

Full rate space-time turbo codes

This paper proposes a class of full space diversity full rate space-time turbo codes. Both parallel concatenated and serially concatenated codes are designed. A rank theory proposed by the authors earlier is employed to check the full space diversity of the codes. The simulations show that the space-time turbo codes can take full advantage of space diversity and time diversity if they are available in the channels. We also study the robustness of performance of both turbo codes and trellis codes in space-time correlated fading channels     

Least-energy path planning and oscillation analysis of robotic manipulator using direct collocation with nonlinear programming

ABSTRACT

Direct collocation is a method that converts a two-point boundary-value problem into a nonlinear programming problem by approximating the state variables and controls into parameters. It has been broadly used in studies of space and orbital mechanics yet has been rarely applied in the fields of robotics. This study builds up a mathematical model of a five-linked manipulator arm. Gradually reducing the upper and lower bounds of the five joint actuator outputs, this paper explores the variations in the least-energy cost function and the final time. Special attention has been focused on whether restrictions would ever arouse any un-anticipated oscillation in the joints. The numerical results show some irony. Excessively restricting the upper and lower output bounds of actuators does not actually gain traction in minimizing the cost index. On the contrary, the value of the cost index is increased by 41.77% from 924.87 to 1310.44 for a tunnel case whose radius is 1.5 m. The simulation cautions that unwanted frequency of oscillation begins to surface due to this wishful restricting. This paper demonstrates how Direct Collocation with Nonlinear Programming can be successfully applied to solve robotic path planning problems. It also cautions the users and designers of the manipulator about the unwanted frequency drift so that the users and designers can amend it before the oscillation builds up.     

rG-CSF reduces endotoxemia and improves survival during E. coli pneumonia

We investigated the effects of recombinant granulocyte colony-stimulating factor (rG-CSF) during canine bacterial pneumonia. Beagles with chronic tracheostomies received daily subcutaneous rG-CSF (5 micrograms/kg body wt) or placebo for 14 days, beginning 9 days before intrabronchial inoculation with E. coli. Animals received antibiotics and fluid support; a subset received humidified oxygen (fractional inspired O2 0.40). Compared with controls, rG-CSF increased circulating neutrophil counts (57.4 vs. 11.0 x 10(3)/mm3, day 1 after infection; P = 0.0001), decreased plasma endotoxin (7.5 vs. 1.1 EU/ml at 8 h; P < 0.01) and serum tumor necrosis factor-alpha (3,402 vs. 729 pg/ml at 2 h; P = 0.01) levels, and prolonged survival (relative risk of death = 0.45, 95% confidence interval 0.21-0.97; P = 0.038). Also, rG-CSF attenuated sepsis-associated myocardial dysfunction (P < 0.001). rG-CSF had no effect on pulmonary function or on blood and lung bacteria counts (all P = not significant). Other animals challenged with endotoxin (4 mg/kg i.v.) after similar treatment with rG-CSF had lower serum endotoxin levels (7.62 vs. 5.81 log EU/ml at 6 h; P < 0.01) and less cardiovascular dysfunction (P < 0.05 to < 0.002) but similar tumor necrosis factor-alpha levels (P = not significant) compared with controls. Thus prophylactic rG-CSF sufficient to increase circulating neutrophils during bacterial pneumonia may improve cardiovascular function and survival by mechanisms that in part enhance the clearance of bacterial toxins but do not improve lung function.     

Case report. Computed tomography of the brain in severe hypoglycaemia

Computed tomographic (CT) findings in a case of extreme hypoglycaemia induced by an overdose of chlorpropamide are described. Brain lesions tend to be preferentially localized along the boundary zones ("watersheds") between the territories of the main cerebral arteries. In our case, generalized brain damage occurred during severe hypoglycaemic coma. Neuropathological changes in this condition have been the subject of previous studies in experimental animals. Computed tomography allows follow-up studies of the human brain damaged by hypoglycaemic coma. Abnormalities revealed by CT probably represent reparative tissue reactions that indirectly reflect the extent of neuronal destruction.     

Reduction of the Positive Organic Artifact on Quartz Filters

Quartz fiber filters are routinely used to collect particulate matter for organic analysis. Such collections may be subject to filtration artifacts: enhancement due to the adsorption of gas-phase organic species or diminishment caused by the volatilization of organic particulate matter. The magnitudes of these competing processes are usually difficult to evaluate separately, although significant amounts of organic carbon on second quartz fiber filters (back filters) downstream of the primary sampling filter indicate that these sampling artifacts are present. In an experiment to reduce the enhancement when sampling organic particulate matter, a diffusive denuder consisting of separated layers of quartz fiber filter was used under the hypothesis that it would selectively remove only those gaseous organic species that normally are retained by the filter medium. This denuder reduced the organic carbon on the back filter by more than a factor of four, to levels comparable to those of the filter blank; the organic carbon on the front filter was reduced by the same absolute amount. The conclusion is that a quartz fiber filter denuder nearly eliminates the enhancement artifact.