The rate distortion behavior of sparse memoryless sources is studied. These serve as models of sparse signal representations and facilitate the performance analysis of "sparsifying" transforms like ...the wavelet transform and nonlinear approximation schemes. For strictly sparse binary sources with Hamming distortion, R(D) is shown to be almost linear. For nonstrictly sparse continuous-valued sources, termed compressible, two measures of compressibility are introduced: incomplete moments and geometric mean. The former lead to low- and high-rate upper bounds on mean squared error D(R), while the latter yields lower and upper bounds on source entropy, thereby characterizing asymptotic R(D) behavior. Thus, the notion of compressibility is quantitatively connected with actual lossy compression. These bounding techniques are applied to two source models: Gaussian mixtures and power laws matching the approximately scale-invariant decay of wavelet coefficients. The former are versatile models for sparse data, which in particular allow to bound high-rate compression performance of a scalar mixture compared to a corresponding unmixed transform coding system. Such a comparison is interesting for transforms with known coefficient decay, but unknown coefficient ordering, e.g., when positions of highest-variance coefficients are unknown. The use of these models and results in distributed coding and compressed sensing scenarios are also discussed.
This paper studies coding schemes for the q -ary symmetric channel based on binary low-density parity-check (LDPC) codes that work for any alphabet size q =2 m , m ∈N, thus complementing some ...recently proposed packet-based schemes requiring large q . First, theoretical optimality of a simple layered scheme is shown; then, a practical coding scheme based on a simple modification of standard binary LDPC decoding is proposed. The decoder is derived from first principles and using a factor-graph representation of a front end that maps q -ary symbols to groups of m bits connected to a binary code. The front end can be processed with a complexity that is linear in m =log 2 q . An extrinsic information transfer chart analysis is carried out and used for code optimization. Finally, it is shown how the same decoder structure can also be applied to a larger class of q -ary channels.
How much blood is needed? Seifried, E.; Klueter, H.; Weidmann, C. ...
Vox sanguinis,
01/2011, Letnik:
100, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Demographic changes in developed countries as their populations age lead to a steady increase in the consumption of standard blood components. Complex therapeutic procedures like haematopoietic stem ...cell transplantation, cardiovascular surgery and solid organ transplantation are options for an increasing proportion of older patients nowadays. This trend is likely to continue in coming years. On the other hand, novel aspects in transplant regimens, therapies for malignant diseases, surgical procedures and perioperative patient management have led to a moderate decrease in blood product consumption per individual procedure. The ageing of populations in developed countries, intra‐society changes in the attitude towards blood donation as an important altruistic behaviour and the overall alterations in our societies will lead to a decline in regular blood donations over the next decades in many developed countries. Artificial blood substitutes or in vitro stem cell‐derived blood components might also become alternatives in the future. However, such substitutes are still in early stages of development and will therefore probably not alleviate this problem within the next few years. Taken together, a declining donation rate and an increase in the consumption of blood components require novel approaches on both sides of the blood supply chain. Different blood donor groups require specific approaches and, for example, inactive or deferred donors must be re‐activated. Optimal use of blood components requires even more attention.
Use of statutory health insurance (SHI) data in health services research is increasing steadily and questions of validity are gaining importance. Using gender-specific diagnosis as an example, the ...aim of this study was to estimate the prevalence of implausible diagnosis and demonstrate an internal validation strategy.
The analysis is based on the SHI data from Baden-Württemberg for 2012. Subject of validation are gender-specific outpatient diagnoses that mismatch with the gender of the insured. To uncover this implausibility, it is necessary to clarify whether the diagnosis or the gender is wrong. The validation criteria used were the presence of further gender-specific diagnoses, the presence of gender-specific settlement items, the specialization of the physician in charge and the gender assignment of the first name of the insured. To review the quality of the validation, it was verified if the gender was changed during the following year.
Around 5.1% of all diagnoses were gender-specific and there was a mismatch between diagnosis and gender in 0.04% of these cases. All validation criteria were useful to sort out implausibility, whereas the last one was the most effective. Only 14% remained unsolved. From the total of 1 145 insured with implausible gender-specific diagnoses, one year later 128 had a new gender (in the data). 119 of these cases were rightly classified as insured with wrong gender and 9 cases were in the unsolved group. This confirms that the validation works well.
Implausibility in SHI data is relatively small and can be solved with appropriate validation criteria. When validating SHI data, it is advisable to question all data used critically, to use multiple validation criteria instead of just one and to abandon the idea that reality and the associated data conform to standardized norms. Keeping these aspects in mind, analysis of SHI data is a good starting point for research in health services.
Day-case biopsy and craniotomy for brain tumours have been reported as safe and feasible options for selected patients. The incidence and timing of complications after such procedures has also been ...characterized in recent publications. However, more widespread adoption of day-case cranial neurosurgery has not taken place. We report the first UK series of day-case surgery for intra-axial tumours, consisting of 30 image-guided biopsies and 11 craniotomies, taking place over 1 year from October 2006. Patients were studied prospectively and 27 30 biopsy and 9 11 craniotomy patients were discharged 6 h postoperatively. One biopsy case was admitted due to increased headache postoperatively, but with a normal CT and one craniotomy case had transient worsening of lower limb paresis requiring overnight admission. The three other overnight admissions were for patient preference. One biopsy patient was readmitted 30 h postoperatively with a seizure and discharged the following day. No patients suffered an adverse outcome. The results are presented together with the Toronto series of 284 cases over 11 years, also with no patients suffering an adverse outcome because of planned early discharge. These results suggest that day-case surgery for brain tumours is a safe and feasible option for patients in the UK.
Background and Objectives Previous studies have shown substantial geographical variation in blood donation within developed countries. To understand this issue better, we identified community ...characteristics associated with blood donor rates in German municipalities in an ecological analysis.
Materials and Methods We calculated an aggregated rate of voluntary blood donors from each of 1533 municipalities in south‐west Germany in 2007 from a database of the German Red Cross Blood Service. A multiple linear regression model estimated the association between the municipality‐specific donor rate and several community characteristics. Finally, a spatial lag regression model was used to control for spatial autocorrelation that occurs when neighbouring units are related to each other.
Results The spatial lag regression model showed that a relatively larger population, a higher percentage of inhabitants older than 30 years, a higher percentage of non‐German citizens and a higher percentage of unemployed persons were associated with lower municipality‐specific donor rates. Conversely, a higher donor rate was correlated with higher voter turnout, a higher percentage of inhabitants between 18 and 24 years and more frequent mobile donation sites.
Conclusions Blood donation appears to be a highly clustered regional phenomenon, suggesting the need for regionally targeted recruiting efforts and careful consideration of the value of mobile donation sites. Our model further suggests that municipalities with a decreasing percentage of 18‐ to 24‐year‐olds and an increasing percentage of older inhabitants may experience substantial declines in future blood donations.
Aims/hypothesis Insulin resistance in skeletal muscle is a hallmark of type 2 diabetes. Therefore, we sought to identify and validate genes involved in the development of insulin resistance in ...skeletal muscle. Materials Differentially regulated genes in skeletal muscle of male obese insulin-resistant, and lean insulin-sensitive Zucker diabetic fatty (ZDF) rats were determined using Affymetrix microarrays. Based on these data, various aspects of glucose disposal, insulin signalling and fatty acid composition were analysed in a muscle cell line overexpressing stearoyl-CoA desaturase 1 (SCD1). Results Gene expression profiling in insulin-resistant skeletal muscle revealed the most pronounced changes in gene expression for genes involved in lipid metabolism. Among these, Scd1 showed increased expression in insulin-resistant animals, correlating with increased amounts of palmitoleoyl-CoA. This was further investigated in a muscle cell line that overexpressed SCD1 and accumulated lipids, revealing impairments of glucose uptake and of different steps of the insulin signalling cascade. We also observed differential effects of high-glucose and fatty acid treatment on glucose uptake and long-chain fatty acyl-CoA profiles, and in particular an accumulation of palmitoleoyl-CoA in cells overexpressing SCD1. Conclusions/interpretation Insulin-resistant skeletal muscle of ZDF rats is characterised by a specific gene expression profile with increased levels of Scd1. An insulin-resistant phenotype similar to that obtained by treatment with palmitate and high glucose can be induced in vitro by overexpression of SCD1 in muscle cells. This supports the hypothesis that elevated SCD1 expression is a possible cause of insulin resistance and type 2 diabetes.
This study investigated in eight healthy male volunteers (a) the gastric emptying pattern of 50 and 100 grams of glucose; (b) its relation to the phase of interdigestive motility (phase I or II) ...existing when glucose was ingested; and (c) the interplay between gastric emptying or duodenal perfusion of glucose (1.1 and 2.2 kcal/min; identical total glucose loads as orally given) and release of glucose-dependent insulinotropic peptide (GIP), glucagon-like peptide-1(7-36)amide (GLP-1), C-peptide, insulin, and plasma glucose. The phase of interdigestive motility existing at the time of glucose ingestion did not affect gastric emptying or any metabolic parameter. Gastric emptying of glucose displayed a power exponential pattern with a short initial lag period. Duodenal delivery of glucose was not constant but exponentially declined over time. Increasing the glucose load reduced the rate of gastric emptying by 27.5% (P < 0.05) but increased the fractional duodenal delivery of glucose. Both glucose loads induced a fed motor pattern which was terminated by an antral phase III when approximately 95% of the meal had emptied. Plasma GLP-1 rose from basal levels of approximately 1 pmol/liter of peaks of 3.2 +/- 0.6 pmol/liter with 50 grams of glucose and of 7.2 +/- 1.6 pmol/liter with 100 grams of glucose. These peaks occurred 20 min after glucose intake irrespective of the load. A duodenal delivery of glucose exceeding 1.4 kcal/min was required to maintain GLP-1 release in contrast to ongoing GIP release with negligibly low emptying of glucose. Oral administration of glucose yielded higher GLP-1 and insulin releases but an equal GIP release compared with the isocaloric duodenal perfusion. We conclude that (a) gastric emptying of glucose displays a power exponential pattern with duodenal delivery exponentially declining over time and (b) a threshold rate of gastric emptying of glucose must be exceeded to release GLP-1, whereas GIP release is not controlled by gastric emptying.
Background
Nerve injury-triggered hyperexcitability in primary sensory neurons is considered a major source of chronic neuropathic pain. The hyperexcitability, in turn, is thought to be related to ...transcriptional switching in afferent cell somata. Analysis using expression microarrays has revealed that many genes are regulated in the dorsal root ganglion (DRG) following axotomy. But which contribute to pain phenotype versus other nerve injury-evoked processes such as nerve regeneration? Using the L5 spinal nerve ligation model of neuropathy we examined differential changes in gene expression in the L5 (and L4) DRGs in five mouse strains with contrasting susceptibility to neuropathic pain. We sought genes for which the degree of regulation correlates with strain-specific pain phenotype.
Results
In an initial experiment six candidate genes previously identified as important in pain physiology were selected for in situ hybridization to DRG sections. Among these, regulation of the Na+ channel α subunit Scn11a correlated with levels of spontaneous pain behavior, and regulation of the cool receptor Trpm8 correlated with heat hypersensibility. In a larger scale experiment, mRNA extracted from individual mouse DRGs was processed on Affymetrix whole-genome expression microarrays. Overall, 2552 ± 477 transcripts were significantly regulated in the axotomized L5DRG 3 days postoperatively. However, in only a small fraction of these was the degree of regulation correlated with pain behavior across strains. Very few genes in the “uninjured” L4DRG showed altered expression (24 ± 28).
Conclusion
Correlational analysis based on in situ hybridization provided evidence that differential regulation of Scn11a and Trpm8 contributes to across-strain variability in pain phenotype. This does not, of course, constitute evidence that the others are unrelated to pain. Correlational analysis based on microarray data yielded a larger “look-up table” of genes whose regulation likely contributes to pain variability. While this list is enriched in genes of potential importance for pain physiology, and is relatively free of the bias inherent in the candidate gene approach, additional steps are required to clarify which transcripts on the list are in fact of functional importance.
PDF
