Post Alignment Research Articles

Enhanced 3D object detection for autonomous driving: A spatial-temporal alignment approach in Bird's Eye View scenarios

This paper presents a novel 3D object detection algorithm designed for Bird's Eye View (BEV) scenarios, which significantly improves detection capabilities by integrating spatial and temporal features. The core of our approach is the spatial-temporal alignment module that efficiently processes information across different time steps and spatial locations, enhancing the precision and robustness of object detection. We employ a temporal self-attention mechanism to capture the motion information of objects over time, allowing the model to correlate features across various time steps for identifying and tracking moving objects. Additionally, a spatial cross-attention mechanism is utilized to focus on spatial features within regions of interest, promoting interactions between features extracted from camera views and BEV queries. Our method also implements temporal feature integration and multi-scale feature fusion to enhance detection stability and accuracy for fast-moving objects and to capture multi-scale context information, respectively. The model employs an enriched feature set post alignment for 3D bounding box prediction, ascertaining the position, dimensions, and orientation of objects. We conducted experiments on two public datasets for autonomous driving nuScenes and Waymo Open Dataset, demonstrating that our method outperforms previous BEVFormer and other state-of-the-art methods in terms of detection accuracy and robustness. The paper concludes with potential future directions for optimizing the BEVFormer model's performance and exploring its application in broader scenarios and tasks.

Commissural alignment in the Evolut TAVR procedure: conventional versus hat marker-guided shaft rotation methods.

Coronary cannulation after TAVR is sometimes difficult due to an overlap between native and neo-commissures, especially in Evolut devices with a supra-annular position. The Evolut C-tab corresponds to a neo-commissure, and the hat marker is in a fixed position. Therefore, the orientation of the hat marker can be adjusted to minimise overlaps. We investigated whether the HAt marker-guided SHaft rotation method (HASH, stylised as the #rotation method) is effective in facilitating coronary artery access after transcatheter aortic valve replacement (TAVR) with an Evolut system. We retrospectively analysed 95 patients who underwent electrocardiogram-gated cardiac computed tomography after TAVR. In the #rotation method, the hat marker of the delivery catheter was adjusted to face the greater curvature of the descending thoracic aorta in the left anterior oblique view. Its orientation was maintained while the system passed through the aortic arch. In total, 60 and 35 patients underwent TAVR with the #rotation and non-#rotation methods, respectively. A ±15° angle between the native and neo-commissures was more frequent in the #rotation group (p=0.001). Favourable angles and appropriate frame orientation for access to the left coronary artery were significantly more frequent in the #rotation group than in the non-#rotation group (p<0.001 and p=0.001). Although the #rotation method showed a higher rate of favourable angles and frames in the right coronary artery, statistically significant differences were not found. The #rotation method is useful for improving commissural post alignment in TAVR with Evolut devices, especially in the ostium of the left coronary artery.

MANAGEMENT OF UNERUPTED ANTERIOR TEETH: AN AUDIT OF TREATMENT OUTCOMES

Introduction: Anterior teeth are valuable for aesthetics, speech and mastication . Their absence, impaction and/or delayed eruption create significant distress often leading to early presentation to the dental office. This study presents an audit of the management of impacted anterior teeth that presented at a tertiary level dental clinic. The periodontal outcomes of the aligned teeth were also reported.&#x0D; Methods: This is an observational study spanning a nine-year period. Demographic data, clinical presentation as well as post alignment dental and periodontal status of the impacted teeth were assessed. Data was analysed using the Statistical Package for Social Sciences (SPSS) version 26. Fisher’s exact test and paired samples T-test were used for categorical and continuous variables respectively. Significance was set at P &lt; 0.05.&#x0D; Results: Twenty-eight (1.76%) cases presenting with failed eruption of thirty-two anterior teeth were found during the period under review. Eight patients were treated by extraction, orthodontic treatment and space closure or prosthetic replacement with a mean treatment time of 2.83 ± 2.66 years. Thirteen patients completed treatment by orthodontic alignment with mean alignment time of 1.4 ± 1.5 years and treatment time of 3.6 ± 2.5 years. There was significant difference in the post-operative root length of aligned teeth compared to their normal antimeres (p &lt; 0.005).&#x0D; Conclusion: Patients with impacted anterior teeth presented later than was beneficial for spontaneous alignment of their teeth. The average 1.5mm loss of root length observed was not detrimental to the anatomical retention or function of the aligned teeth. There is need for more enlightenment with regards to early presentation for dental problems to avoid expensive and time-consuming treatments.

Evaluation of pain, alignment efficiency, and post alignment anterior torque between I –Archwires and superelastic NiTi wires: A comparative study

: to compare the aligning efficiency, pain experienced by the patient during alignment and the post alignment third order values of anterior teeth in I arch (study) group and conventional NiTi (control) wire group.: A prospective clinical study.: A total of 40 dental arches (maxilla/mandible) were divided into 2 study groups with 20 dental arches (maxilla/mandible) in each group based on the selection criteria. Group I. Twenty dental arches (maxillary/mandibular) having 0.018” preadjusted appliance (MBT) brackets (ORMCO), aligned with I –arch 0.016”x0.014” copper NiTi wires. Group II. Twenty dental arches (maxillary/mandibular) having 0.018” preadjusted appliance (MBT) brackets by ORMCO aligned with round super elastic NiTi archwires.: I -arch copper NiTi (study group) was more efficient in alignment compared to the superelastic NiTi (control group) in the lower arch and the values are statistically significant. There was torque expression in the I-arch group as compared to the superelastic NiTi group. The subjects in the I-arch (study group) experienced lesser pain compared to the superelastic NiTi (control group) and the pain values are statistically significant.

Comparison of palatal depth and intermolar width in class I and class II div 1 malocclusion and in class II div 1 with hyperdivergent and hypodivergent pattern

: To compare the aligning efficiency, pain experienced by the patient during alignment and the post alignment third order values of anterior teeth in I arch (study) group and conventional NiTi (control) wire group.: A prospective clinical study.: A total of 40 dental arches (maxilla/mandible) were divided into 2 study groups with 20 dental arches (maxilla/mandible) in each group based on the selection criteria. Group I. Twenty dental arches (maxillary/mandibular) having 0.018” preadjusted appliance (MBT) brackets (ORMCO), aligned with I –arch 0.016”x0.014” copper NiTi wires. Group II Twenty dental arches (maxillary/mandibular) having 0.018” preadjusted appliance (MBT) brackets by ORMCO aligned with round super elastic NiTi archwires.: I -arch copper NiTi (study group) was more efficient in alignment compared to the superelastic NiTi (control group) in the lower arch and the values are statistically significant. There was torque expression in the I-arch group as compared to the superelastic NiTi group. The subjects in the I-arch (study group) experienced lesser pain compared to the superelastic NiTi (control group) and the pain values are statistically significant.

SRAMM: Short Read Alignment Mapping Metrics

Short Read Alignment Mapping Metrics (SRAMM): is an efficient and versatile command line tool providing additional short read mapping metrics, filtering, and graphs. Short read aligners report MAPing Quality (MAPQ), but these methods generally are neither standardized nor well described in literature or software manuals. Additionally, third party mapping quality programs are typically computationally intensive or designed for specific applications. SRAMM efficiently generates multiple different concept-based mapping scores to provide for an informative post alignment examination and filtering process of aligned short reads for various downstream applications. SRAMM is compatible with Python 2.6+ and Python 3.6+ on all operating systems. It works with any short read aligner that generates SAM/BAM/CRAM file outputs and reports 'AS' tags. It is freely available under the MIT license at http://github.com/achon/sramm.

Automating and Extending Comprehensive Two-Dimensional Gas Chromatography Data Processing by Interfacing Open-Source and Commercial Software.

Comprehensive two-dimensional gas chromatography (GC×GC) is a powerful analytical tool for both nontargeted and targeted analyses. However, there is a need for more integrated workflows for processing and managing the resultant high-complexity datasets. End-to-end workflows for processing GC×GC data are challenging and often require multiple tools or software to process a single dataset. We describe a new approach, which uses an existing underutilized interface within commercial software to integrate free and open-source/external scripts and tools, tailoring the workflow to the needs of the individual researcher within a single software environment. To demonstrate the concept, the interface was successfully used to complete a first-pass alignment on a large-scale GC×GC metabolomics dataset. The analysis was performed by interfacing bespoke and published external algorithms within a commercial software environment to automatically correct the variation in retention times captured by a routine reference standard. Variation in 1tR and 2tR was reduced on average from 8 and 16% CV prealignment to less than 1 and 2% post alignment, respectively. The interface enables automation and creation of new functions and increases the interconnectivity between chemometric tools, providing a window for integrating data-processing software with larger informatics-based data management platforms.

Abstract 5881: Assessment of two whole transcriptome RNA sequencing library preparation Illumina workflows in FFPE human specimens with suboptimal quality

Abstract Purpose High analytical sensitivity and a broad dynamic range make RNA sequencing (RNA-Seq) an appealing platform for mRNA expression analyses for clinical exploratory biomarker development and identification. However, the reliability and accuracy of RNA-Seq data rely on the input RNA template quality and quantity. Additionally, cDNA library preparation methods can significantly influence the results, especially in samples with suboptimal quality such as those originating from FFPE specimens. Here we compared two Illumina library preparation methods for RNA-Seq analysis using several FFPE samples from human cancer indications at two independent vendors. Study Procedure Twenty-five FFPE samples from 5 indications (NSCLC, CRC, RC, BC and HCC) were used, covering a wide range of sample storage (3-25 years-old), sample qualities, and specimen types (resection vs. core needle biopsy). Each sample was processed independently by both vendors. Total RNA was isolated using the Qiagen miRNeasy FFPE kit followed by library construction using either TruSeq Stranded Total RNA library preparation kit with Ribo-Zero Gold, or TruSeq RNA Access library preparation kit. Libraries were normalized to 20pM and sequenced on an Illumina HiSeq 2500 using V3 chemistry, in paired-end mode with a read length of 2 × 50bp. The data were processed through a standard RNASeq pipeline to produce counts and transcripts per millions (TPMs) for each gene in each sample to compare two library kits at two different vendors. Data Summary QC data for FFPE RNA extraction, library preparation and sequencing generated by the two vendors are comparable, and sequencing results show high concordance as well. With the TruSeq Total kit, the average spearman correlation between vendors was 0.87 and the average Pearson correlation was 0.76. With the Access kit, the average spearman correlation between vendors was 0.89 and the average Pearson correlation was 0.73. Illumina TruSeq RNA Access Library generates more reads from protein coding genes than the Illumina TruSeq Stranded kit and generated acceptable sequencing results at both vendors in all usable samples (15/20), based on post alignment QC mapping to a reference genome (&amp;gt;90%). Conclusion Our analyses provide evidence to guide selection of sequencing methods for studies in which the sample quality is severely compromised. The comparison results demonstrate that the Illumina RNA Access library protocol more efficiently targets protein coding genes than TruSeq Stranded Total RNA library protocol on highly degraded FFPE samples and can be an attractive alternative for clinical trial studies in which the FFPE quality is severely compromised. However, since the probe selection step in the RNA Access protocol may bias results compared to other platforms, further exploration may be needed. Citation Format: Danyi Wang, Alex Rolfe, Alice Huang, Dennis O'Rourke, Juergen Scheuenpflug, Zheng Feng. Assessment of two whole transcriptome RNA sequencing library preparation Illumina workflows in FFPE human specimens with suboptimal quality [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5881.

A Massive, Late Neolithic Pit Structure associated with Durrington Walls Henge

A series of massive geophysical anomalies, located south of the Durrington Walls henge monument, were identified during fluxgate gradiometer survey undertaken by the Stonehenge Hidden Landscapes Project (SHLP). Initially interpreted as dewponds, these data have been re-evaluated, along with information on similar features revealed by archaeological contractors undertaking survey and excavation to the north of the Durrington Walls henge. Analysis of the available data identified a total of 20 comparable features, which align within a series of arcs adjacent to Durrington Walls. Further geophysical survey, supported by mechanical coring, was undertaken on several geophysical anomalies to assess their nature, and to provide dating and environmental evidence. The results of fieldwork demonstrate that some of these features, at least, were massive, circular pits with a surface diameter of 20m or more and a depth of at least 5m. Struck flint and bone were recovered from primary silts and radiocarbon dating indicates a Late Neolithic date for the lower silts of one pit. The degree of similarity across the 20 features identified suggests that they could have formed part of a circuit of large pits around Durrington Walls, and this may also have incorporated the recently discovered Larkhill causewayed enclosure. The diameter of the circuit of pits exceeds 2km and there is some evidence that an intermittent, inner post alignment may have existed within the circuit of pits. One pit may provide evidence for a recut; suggesting that some of these features could have been maintained through to the Middle Bronze Age. Together, these features represent a unique group of features related to the henge at Durrington Walls, executed at a scale not previously recorded.

Abstract 818: Refining and assessing quality for next generation sequencing of formalin-fixed, paraffin-embedded tissues.

Abstract With increasing acceptance of the use of formalin-fixed, paraffin-embedded (FFPE) for next generation sequencing (NGS), researchers and clinicians need to choose whether to analyze FFPE or cryopreserved (CRYO) tissue. In many clinical situations normal tissue would be available from blood, FFPE normal and tumor tissues from pathology archives, while fresh or CRYO tumor would require an invasive biopsy. Options include analysis of either CRYO or FFPE tumor coupled with either CRYO or FFPE normal tissue. Alternately, analyses could incude both CRYO and FFPE normal tissue to detect the impact of FFPE on NGS results, or could defer analysis of normal tissue with identification of novel mutations by comparisons of variants in tumor with SNP databases. Little data are available directly comparing results or tradeoffs resulting from these choices, prompting this study comparing NGS analysis of matched samples of normal CRYO and FFPE and tumor CRYO and FFPE. Appropriate kits from Qiagen were used to extract DNA from sections of CRYO and FFPE tissues of bladder cancers obtained from our institution's biorepository with informed consent. Libraries were constructed using Agilent library kits and targeted with SureSelect Kinome reagents. Libraries were sequenced by 100 bp paired end Illumina sequencing on a HiSeq. Our analysis pipeline used BWA for alignment and conducted subsequent analyses in GeneSpring NGS 12.1, including inspecting tile quality, removing duplicates, filtering on base quality, post alignment read (alignment score 95 and mapping quality 40 or above), and read status (mate near required). Comparing a representative specimen of tumor CRYO with tumor FFPE, targeted sequencing library preparations yielded 19.9 and 12.8 million reads for CRYO and FFPE respectively. For this analysis filtering by tile quality was not required. Uniquely mapped reads to human genome were 92% of CRYO and 86% of FFPE. Out of the total reads that aligned, 73.5% of CRYO and 74.3% of FFPE reads aligned without error. Post all filters, 39% of CRYO and 44% of FFPE reads were available for variant calling. Comparing variant calls from reference sequence to novel variants, there were no differences comparing normal CRYO vs normal FFPE, or tumor CRYO vs tumor FFPE. Comparing tumor with normal samples there were 30 variants for CRYO samples, 25 for FFPE samples, and 23 when CRYO normal was compared with FFPE tumor. In comparing normal vs tumor, 22 variants calls were the same for all comparisons of tissue types. Results will be presented for a more detailed analyses of multiple samples Overall we found high concordance between results from the CRYO and FFPE samples. Our results support use of FFPE for NGS of clinical samples and highlights potential contribution of including sequencing a normal cryropreserved specimen to ensure analysis quality. Citation Format: Umar Farooq, Michael J. Gooch, Linda Burian, Prashant Singh, Shirin Karimi, Lorrie A. Perpetua, Mary M. Sanders, Richard B. Everson. Refining and assessing quality for next generation sequencing of formalin-fixed, paraffin-embedded tissues. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 818. doi:10.1158/1538-7445.AM2013-818

Building an optimized pipeline for whole-exome sequencing

Motivations. Managing the huge amount of data produced by NGS platforms requires non trivial IT skills. Furthermore the wide list of freely available analytical tools for NGS data analysis makes difficult to choose easily the pipeline components. An additional layer of complexity is due to the need of integrate all steps in a single analysis: the best tool for a specific purpose could be incompatible with other tools of the pipeline, i.e. a tool performing a statistical calculation when raw data are required for the next step. In case of a whole exome analysis building effective pipelines that relate variants to their samples and controls, annotate them from multiple sources requires a large customization effort. Methods. Our proposed pipeline walks through several steps to perform a full analysis. 1) Before mapping the short-reads against the reference genome, a pre-process is necessary. FastQ files should be checked for integrity and cleaned up from any unwanted symbols that can alter any NGS tool behavior. Quality checks can be pursued with tools like FastQC to ensure that sequences provided reach the minimum level of mean quality necessary for a complete analysis. 2) Alignment is usually performed with BWA [1], which is capable of finding gaps. It results to be a good compromise between speed and accuracy. When there are known problems in the sequence provided, e.g. FastQC outlines a poor quality in the last or first bases sequenced, other tools can perform a more sensible alignment at a lower speed. 3) BWA provides mapping results in SAM format [2]. This is the most widely used format for alignment output. This text-based format should be converted into its binary equivalent BAM format through the SAMtools; BAM can be indexed and sorted to enable faster operations at subsequent steps. 4) Before searching any variant in mapping binary data, some other editing are required to prevent artifacts in results. Quality recalibration is required to refine some oddness caused by sequencing and mapping on quality scores. Duplicates are in most of the case result of PCR amplification and should be avoided as they lead to false positives. A re-alignment around known indels position should be also carried on to delete other artifacts. 5) Single Nucleotide Polymorphism (SNP, a single nucleotide occurring in one member is replaced by another nucleotide in the other member) and Deletion-Insertion Polymorphism (DIP, refers to the fact that a short nucleotide sequence in one member is omitted in the other member) can be now called from the mapping data obtained from the previous 4 steps. 6) SNP and DIP obtained have various score to consider to ensure a minimum depth coverage and quality score in order to remove any false positive in the list. 7) When dealing with multiple WES data lanes, the usual scenario is a combination of affected/unaffected tissue samples. In this case a critical information is about the haplotype phasing, which allow discovering complex heterozygous or homologous mutations. 8) The last critical aspect of variants calling is to associate as many annotation as possible to the variant list i.e. annotation stored in database like dbSNP, 1000genomes, etc. After these steps data can be saved into custom databases to allow cross-linking and intersections, statistics and much more. Results. We have tested different freely available algorithms used at the alignment and post alignment stage and integrated them with custom-build scripts to provide the most suitable and complete combination to create significant whole exome dataset results. Hence, we have customized the whole-exome data analysis pipeline to preferentially held true variants by minimizing the incidence of false positives and providing the benchmarks for the best choice of right analytical tools.

Customisation of the Exome Data Analysis Pipeline Using a Combinatorial Approach

The advent of next generation sequencing (NGS) technologies have revolutionised the way biologists produce, analyse and interpret data. Although NGS platforms provide a cost-effective way to discover genome-wide variants from a single experiment, variants discovered by NGS need follow up validation due to the high error rates associated with various sequencing chemistries. Recently, whole exome sequencing has been proposed as an affordable option compared to whole genome runs but it still requires follow up validation of all the novel exomic variants. Customarily, a consensus approach is used to overcome the systematic errors inherent to the sequencing technology, alignment and post alignment variant detection algorithms. However, the aforementioned approach warrants the use of multiple sequencing chemistry, multiple alignment tools, multiple variant callers which may not be viable in terms of time and money for individual investigators with limited informatics know-how. Biologists often lack the requisite training to deal with the huge amount of data produced by NGS runs and face difficulty in choosing from the list of freely available analytical tools for NGS data analysis. Hence, there is a need to customise the NGS data analysis pipeline to preferentially retain true variants by minimising the incidence of false positives and make the choice of right analytical tools easier. To this end, we have sampled different freely available tools used at the alignment and post alignment stage suggesting the use of the most suitable combination determined by a simple framework of pre-existing metrics to create significant datasets.

A Late Prehistoric Timber Alignment in the Waveney Valley, Suffolk: Excavations at Barsham Marshes

This paper describes the results of excavations and associated palaeoenvironmental analyses at Barsham Marshes, Suffolk, England. The site is a triple post alignment of oak stakes built at the edge of a palaeochannel of the River Waveney. The alignment has been traced for over 30 m but neither terminus of the site has been excavated. Dendrochronological dating of the timbers has produced a range of felling dates between 8 BC and AD 8 indicating a late Iron Age date for the structure. No other cultural material was recovered. Palaeoenvironmental analyses of the associated deposits indicate that the site was located at the edge of a shallow channel of the River Waveney with local aquatic and alder carr vegetation and evidence for more open scrub and pastoral environments in the wider landscape. This channel appears to have infilled by the 11th century AD and is overlain by a thin layer of humified peat, corresponding to the uppermost level of preservation of the stakes. It is likely that any superstructure originally supported by the stakes had finally decomposed or been dismantled by this time. The site is compared to that of Beccles some 3 km down river where excavations have revealed a triple post alignment also dating to the late Iron Age but with evidence for activity during the Romano-British period. The possible form and function(s) of the sites are discussed.

Beccles Triple Post Alignment, Beccles Marshes, Suffolk: Excavation and Palaeoenvironmental Analyses of an Iron Age Wetland Site

This paper describes the results of two seasons of excavation and associated palaeoenvironmental analyses of a wetland site on Beccles Marshes, Beccles, Suffolk. The site has been identified as a triple post alignment of oak timbers (0.6–2.0 m long), over 100 m in length, and 3–4 m wide, running north-west to south-east towards the River Waveney. It was constructed in a single phase which has been dated dendrochronologically to 75 BC, although discrete brushwood features identified as possible short trackways have been dated by radiocarbon to both before and after the alignment was built. It is unclear if the posts ever supported a superstructure but notches (‘halving lap joints’) in some of the posts appear to have held timbers to support the posts and/or aid in their insertion. In addition, fragments of both Iron Age and Romano-British pottery were recovered. A substantial assemblage of worked wooden remains appears to reflect the construction of the post row itself and perhaps the on-site clearance of floodplain vegetation. This assemblage also contains waste material derived from the reduction splitting of timbers larger than the posts of the alignment, but which have not been recovered from the site. Environmental analyses indicate that the current landscape context of the site with respect to the River Waveney is probably similar to that which pertained in prehistory. The coleoptera (beetle) record illustrates a series of changes in the on-site vegetation in the period before, during and after the main phase of human activity which may be related to a range of factors including floodplain hydrology and anthropogenic utilisation of Beccles Marshes. The possible form and function of the site is discussed in relation to the later prehistoric period in Suffolk.

The Effects of Strabismus on Motor Development

IntroductionBlindness in young children has been shown to lead to significant motor delay. Few studies to date have evaluated the effects of strabismus and its treatment on motor development.MethodsWe evaluated nine children prior to and post eye alignment via strabismus surgery to determine the effect of this treatment on motor development. Developmental milestones using the Bayley and modified Denver developmental scale were recorded prior to and post surgery.ResultsIt was found that in this study sample there was developmental advancement within days of surgery in every case.ConclusionWe feel that eye alignment at an early age in strabismic children is an important factor contributing to age appropriate motor development as measured by developmental milestones. A method for a larger scale objective study to better define the effect of strabismus surgery on motor development is currently being planned.

Multi-layered PZT/polymer composites to increase signal-to-noise ratio and resolution for medical ultrasound transducers part II: thick film technology.

Increasing transducer bandwidth and signal-to-noise ratio (SNR) is fundamental to improving the quality of medical ultrasound images. In previous work, we have proposed the use of multi-layer 1-3 PZT/polymer composites to increase both, but have encountered significant fabrication challenges [19]. These difficulties include making the bond thickness between the layers small relative to the ultrasound wavelength and aligning the posts of the composite to increase coupling coefficient. Thus, we have developed a multi-layer composite hybrid array that will not require post alignment. Starting from a 2-MHz, three-layer PZT-5H, thick film transducer designed for 1.5-D arrays, cuts are made only through the top layer and back-filled with epoxy, forming a composite layer on top of two ceramic layers. Finite element (PZFlex) simulations show that for a 2-MHz phased-array element with a single matching layer, the three-layer hybrid structure increases the pulse echo SNR by 11 dB versus a single layer PZT element and improves -6 dB pulse echo fractional bandwidth by a factor of 1.4. Composite hybrid arrays fabricated in our laboratory showed an improvement in SNR of 6 to 11 dB over a PZT control and an increase in -6 dB bandwidth by a factor of 1.1. Images from a phased-array scanner confirmed these improvements.

Multi-layered PZT/polymer composites to increase signal-to-noise ratio and resolution for medical ultrasound transducers

Increasing transducer bandwidth and signal-to-noise ratio (SNR) is fundamental to improving the quality of medical ultrasound images. In previous work, the authors have proposed the use of multi-layer 1-3 PZT/epoxy composites to increase both but have encountered significant fabrication challenges. These difficulties include making the bond thickness between the layers extremely small relative to the ultrasound wavelength and aligning the posts of the composite to increase the coupling coefficient. The authors have routinely achieved a bond thickness of less than 5 mum but aligning the posts is more complicated. Finite element (PZFlex; Weidlinger, Assoc., New York, NY and Los Altos, CA) simulations show that the pulse-echo SNR and bandwidth degrade significantly with misalignment of the posts. Alignment of greater than 90% of the post pitch (i.e., tolerance of 10 to 20 mum) is required to obtain significant increases in SNR and bandwidth relative to conventional transducer arrays. This will be a difficult tolerance for large-scale production. Thus, the authors have developed a multi-layer composite hybrid array that will not require post alignment. This structure consists of a layer of 5 MHz 1-3 composite material on top of conventional 5 MHz PZT, which will provide greater SNR relative to conventional composites and increased bandwidth over multi-layer PZT. PZFlex simulations show that for a 2 MHz linear array element, the 2 layer hybrid structure increases the pulse-echo SNR by 7.5 dB over that from a single layer PZT element. Even without a matching layer, an increase in the -6 dB pulse-echo fractional bandwidth from 22% for the PZT element to 35% for the hybrid element was also predicted. Experimentally, in a 32 element array, the authors achieved an increase of 5.2 dB in SNR and an increased -6 dB bandwidth from 23 to 30%. In vitro and in vivo images showed corresponding improvements.

Bone remains from Flag Fen platform and Fengate Power Station post alignment

The bone assemblages from the Flag Fen platform itself and from the contemporary post alignment revealed at the Fengate Power Station site are small (respectively c. 150 and c. 600 identified pieces), but may nonetheless shed some light on the nature of human activity at the two sites. For obvious reasons, this study is principally directed towards understanding the circumstances of bone deposition rather than towards a reconstruction of local animal husbandry.