Robustly good trellis codes

The relationship between the distance properties of trellis codes and the computational effort and error performance of sequential decoding is studied and optimum distance profile (ODP) and optimum free distance (OFD) trellis codes are constructed for 8-PSK and 16 QAM modulation. A comparison of the performance of both the ODP and the OFD trellis codes reveals that neither class of codes results in the best trade-off between error performance and computational effort when sequential decoding is used. A new algorithm is then proposed to construct robustly good trellis codes for use with sequential decoding. New trellis codes with asymptotic coding gains up to 6.66 dB are obtained using this algorithm, and the new codes achieve nearly the same free distances as the OFD codes and nearly the same distance profiles as the ODP codes     

An overview of FDA medical device regulation as it relates to deep brain stimulation devices.

The United States Food and Drug Administration (FDA) is charged with assuring the safety and effectiveness of a variety of medical products and the FDA's Center for Devices and Radiological Health is responsible for premarket and postmarket regulation of medical devices. In this paper, we review--from device classification and clinical studies to the final marketing application--FDA's premarket requirements and postmarket requirements as they relate to deep brain stimulation devices.     

Life events and post-traumatic stress: the development of a new measure for children and adolescents

BACKGROUND: A new interview measure of life events and post-traumatic stress disorder (PTSD) has been developed for children and adolescents aged 9 through 17, for use in both epidemiological and clinical studies. It includes 'high magnitude' events associated with PTSD as well as other 'low magnitude' events. METHOD: The interview is designed as a module of the Child and Adolescent Psychiatric Assessment, an interviewer-based interview conducted with parent and child separately by trained lay interviewers. The module includes: (1) questions about a wide range of events; (2) a screen for key PTSD symptoms (painful recall, avoidance, hypervigilance); and (3) a detailed interview on all PTSD symptoms, including onset, duration, severity and co-morbidity. A test-retest reliability study was conducted with 58 parents and children, who were interviewed twice by different interviewers. RESULTS: Intraclass correlations were 0.72 (child) and 0.83 (parent) for high magnitude events, and 0.62 (child) and 0.58 (parent) for low magnitude events. Kappa coefficients ranged from high for violence and sexual abuse to low for child reports of serious accidents and natural disasters. The reliability of the PTSD screen symptoms was fair to excellent (kappa = 0.40-0.79), and reliability of PTSD symptoms in those who passed the screen was excellent (ICC = 0.94-0.99). Compared with a general population sample (N = 1015), the clinic-referred subjects and their parents were twice as likely to report a traumatic event and, depending on the event, up to 25 times as likely to report symptoms of PTSD. CONCLUSIONS: The results support the reliability and discriminant validity of the measure.     

Thermal analysis of polymer–water interactions and their relation to gas hydrate inhibition

Gas hydrates formed in oil production pipelines are crystalline solids where hydrocarbon gas molecules such as methane, propane, and their mixtures are trapped in a cagelike structure by hydrogen‐bonded water molecules to form undesirable plugs. Methanol and glycol are currently used to prevent these plugs via thermodynamic inhibition. Small amounts of water‐soluble polymers may provide an alternate approach for preventing gas hydrates. In this study, we expand the fundamental understanding of water–polymer systems with differential scanning calorimetry. Nonfreezable bound water was used to quantify polymer–water interactions and relate them to the chemical structure for a series of polymers, including acrylamides, cyclic lactams, and n‐vinyl amides. For good interactions, the water structure needs to be stabilized through hydrophobic interactions. An increased hydrophobicity of the pendant group also appears to favor polymer performance as a gas hydrate inhibitor. Good inhibitors, such as poly(diethyl acrylamide) and poly(N‐vinyl caprolactam), also show higher heat capacities, which indicate higher hydrophobicity, than poor performers such as polyzwitterions, in which hydrophilicity dominated. The phase behavior and thermodynamic properties of dilute polymer solutions were also evaluated through measurements of the heat of demixing and lower critical solution temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2642–2653, 2007     

Carbohydrate molecular weight profiling, sequence, linkage, and branching data: ES-MS and CID

This section summarizes several strategies for a more complete understanding of carbohydrate structure with a focus on glycolipids and glycoprotein glycans. The techniques include periodate oxidation to impart greater molecular specificity to isomeric glycans, methylation to improve sensitivity and the information content within CID spectra, electrospray for "soft" and efficient ionization, and CID to obtain structural detail. The lipophilicity of the products following derivatization contributes to product cleanup by solvent extraction and enhances sensitivity during ES. When combined with CID information, this yields sequence, linkage, and branching information. Oxidation and reduction preceding methylation augments CID analysis with an altered structure that can be profiled at the same sensitivity. Within the context of established motifs, these contrasting profiles corroborate glycan structure and specifically identify isobaric elements transparent in the initial profile. An earlier report indicating ring-opening fragments were essentially absent in low-energy collisions of methylated and natriated oligosaccharides contrasts our observations. However, as this report used a methylated oligomer containing an internal N-acetylhexose as an illustration, the conclusion is plausible (cf., Figure 9). The poor ionization efficiency of FAB and the high matrix background limit the dynamic range in the CID spectrum and, thereby, the ability to unambiguously identify weaker peaks. It would be expected that high-energy CID affords a broader range of fragment types, including ring-opening fragments. In terms of a structural methodology, this is ambivalent since the increase in fragmentation pathways also applies to small molecule eliminations which are usually less informative. In ES-CID-MS, the carbohydrate chemist has a powerful new tool in hand for structural elucidations that can be conducted at the low-picomole level. Parallel developments can be expected to continue for other ionization methods, in particular matrix-assisted desorption/ionization on linear and reflectron time of flight mass spectrometers, and improvement in the performance and sensitivity of high-resolution mass analyzers through the use of focal plane detectors and more sophisticated hardware and software for Fourier transform ion cyclotron resonance mass measurements. These have, as yet, only begun to be applied to carbohydrate structural analysis but should add still more versatility to experimental design in the future.     

The pancreatic cancer proteome - recent advances and future promise

Of the common cancers, pancreatic ductal adenocarcinoma is one of the most lethal. The cancer's aggressive biology, leading to rapid dissemination, combined with a lack of clearly recognisable symptoms means that for many patients, the disease is at an advanced stage when diagnosed. The prognosis is consequently very poor, with as few as 3-5% of patients surviving 5?years. Recently, proteomic technologies have been employed in an effort to identify protein biomarkers, therapeutic targets and disease response markers for pancreatic cancer. Research has primarily relied upon pancreatic tissue samples, and body fluids such as pancreatic juice and blood serum. In this article, we will highlight the current proteomic techniques, qualitative and quantitative, employed in the field of pancreatic cancer research. We will review both the progress made and the challenges ahead, in elaborating the biology of pancreatic cancer and identifying novel biomarkers.     

Electrodeposition of copper into high aspect ratio PCB micro-via using megasonic agitation

This paper presents the use of micro-particle imaging velocimetry (micro-PIV) to analyse fluid flow and hence ion replenishment in PCB micro-via during the electroplating process. The cross section of a PCB via is fabricated in PMMA to allow optical access to the sample. Fluid flow within two 1:1 aspect ratio blind micro-vias, one with straight side walls and the other with tapered side walls were compared. Flow is also analysed in a 1:1 aspect ratio through via. Flow rates measured using micro-PIV are used to validate simulated flow models. The results show that there are increased flow rates within the blind via with tapered side walls. This goes some way to explaining the improved electroplating results obtained in industry when tapered vias are used. Initial experimental results using megasonic streaming to remove bubbles from blind micro-via and promote ion transportation within high aspect ratio PCB micro-via to enhance electrodeposition are also reported.