bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact de la COVID-19 sur les services de prévention du VIH et de prise en charge des personnes vivant avec le VIH dans la ville de Bukavu : une étude mixte séquentielle explicative
Authors: Kajiramugabi François Maneraguha , Chirimwami Patrick Murhula , Côté José , Mouala Christian , Rothan-Tondeur Monique , Margat Aurore
Published: January 2024

Introduction : Depuis son apparition fin 2019 en Chine, les mesures de riposte contre l’infection à COVID-19 ont perturbé la prestation des services de santé primaires dont ceux liés au virus de l’immunodéficience humaine (VIH). En République démocratique du Congo, l’effet des mesures anti-COVID-19 (confinement) sur l’utilisation des services de prévention du VIH et de prise en charge des personnes vivant avec le VIH (PVVIH) reste peu décrit à ce jour.

Objectif : Comparer et comprendre l’effet des mesures anti-COVID-19 sur l’utilisation des services préventifs du VIH et de prise en charge des PVVIH dans les Centres de traitement ambulatoire (CTA) de Bukavu avant (octobre 2019 à février 2020) et pendant (mars à juillet 2020) la période des mesures anti-COVID-19.

Méthodes : Étude mixte multisite avec un devis séquentiel explicatif réalisée à Bukavu entre juillet et septembre 2021. La phase quantitative est observationnelle, descriptive, rétrospective et basée sur des données programmatiques issues des CTA. La phase qualitative, guidée par les résultats quantitatifs, est basée sur 31 entretiens semi-structurés avec les soignants et les PVVIH.

Résultats : Par comparaison avec la période pré-COVID-19, les mesures anti-COVID-19 ont entrainé une baisse de 11 à 20% des services de prévention du VIH et de prise en charge des PVVIH. Elles ont également induit les ruptures de stock d’antirétroviraux et de tests VIH, la réorganisation des services VIH, la contamination de certains soignants à la COVID-19 et le décès d’autres, ainsi qu’une baisse de l’utilisation des services VIH.

Discussion et conclusion : À Bukavu, les mesures anti-COVID-19 ont eu un impact négatif sur le parcours de soins des personnes à risque et infectées par le VIH. Elles ont entravé les progrès vers les objectifs : 95% des personnes dépistées au VIH, 95% des PVVIH sous traitement et 95% des PVVIH avec une charge virale supprimée.
Tempo and mode of gene expression evolution in the brain across primates
Authors: Rickelton Katherine , Zintel Trisha M , Pizzollo Jason , Miller Emily , Ely John J , Raghanti Mary Ann , Hopkins William D , Hof Patrick R , Sherwood Chet C , Bauernfeind Amy L , Babbitt Courtney C
Published: January 2024

Primate evolution has led to a remarkable diversity of behavioral specializations and pronounced brain size variation among species (Barton, 2012; DeCasien and Higham, 2019; Powell et al., 2017). Gene expression provides a promising opportunity for studying the molecular basis of brain evolution, but it has been explored in very few primate species to date (e.g. Khaitovich et al., 2005; Khrameeva et al., 2020; Ma et al., 2022; Somel et al., 2009). To understand the landscape of gene expression evolution across the primate lineage, we generated and analyzed RNA-seq data from four brain regions in an unprecedented eighteen species. Here, we show a remarkable level of variation in gene expression among hominid species, including humans and chimpanzees, despite their relatively recent divergence time from other primates. We found that individual genes display a wide range of expression dynamics across evolutionary time reflective of the diverse selection pressures acting on genes within primate brain tissue. Using our samples that represent a 190-fold difference in primate brain size, we identified genes with variation in expression most correlated with brain size. Our study extensively broadens the phylogenetic context of what is known about the molecular evolution of the brain across primates and identifies novel candidate genes for the study of genetic regulation of brain evolution.
Association of genetic variation in COL11A1 with adolescent idiopathic scoliosis
Authors: Yu Hao , Khanshour Anas M , Ushiki Aki , Otomo Nao , Koike Yoshinao , Einarsdottir Elisabet , Fan Yanhui , Antunes Lilian , Kidane Yared H , Cornelia Reuel , Sheng Rory R , Zhang Yichi , Pei Jimin , Grishin Nick V , Evers Bret M , Cheung Jason Pui Yin , Herring John A , Terao Chikashi , Song You-qiang , Gurnett Christina A , Gerdhem Paul , Ikegawa Shiro , Rios Jonathan J , Ahituv Nadav , Wise Carol A
Published: January 2024

Adolescent idiopathic scoliosis (AIS) is a common and progressive spinal deformity in children that exhibits striking sexual dimorphism, with girls at more than fivefold greater risk of severe disease compared to boys. Despite its medical impact, the molecular mechanisms that drive AIS are largely unknown. We previously defined a female-specific AIS genetic risk locus in an enhancer near the PAX1 gene. Here, we sought to define the roles of PAX1 and newly identified AIS-associated genes in the developmental mechanism of AIS. In a genetic study of 10,519 individuals with AIS and 93,238 unaffected controls, significant association was identified with a variant in COL11A1 encoding collagen (α1) XI (rs3753841; NM_080629.2_c.4004C>T; p.(Pro1335Leu); p=7.07E–11, OR = 1.118). Using CRISPR mutagenesis we generated Pax1 knockout mice (Pax1-/-). In postnatal spines we found that PAX1 and collagen (α1) XI protein both localize within the intervertebral disc-vertebral junction region encompassing the growth plate, with less collagen (α1) XI detected in Pax1-/- spines compared to wild-type. By genetic targeting we found that wild-type Col11a1 expression in costal chondrocytes suppresses expression of Pax1 and of Mmp3, encoding the matrix metalloproteinase 3 enzyme implicated in matrix remodeling. However, the latter suppression was abrogated in the presence of the AIS-associated COL11A1P1335L mutant. Further, we found that either knockdown of the estrogen receptor gene Esr2 or tamoxifen treatment significantly altered Col11a1 and Mmp3 expression in chondrocytes. We propose a new molecular model of AIS pathogenesis wherein genetic variation and estrogen signaling increase disease susceptibility by altering a PAX1-COL11a1-MMP3 signaling axis in spinal chondrocytes.
Feedback inhibition by a descending GABAergic neuron regulates timing of escape behavior in Drosophila larvae
Authors: Zhu Jiayi , Boivin Jean-Christophe , Garner Alastair , Ning Jing , Zhao Yi Q , Ohyama Tomoko
Published: January 2024

Escape behaviors help animals avoid harm from predators and other threats in the environment. Successful escape relies on integrating information from multiple stimulus modalities (of external or internal origin) to compute trajectories toward safe locations, choose between actions that satisfy competing motivations, and execute other strategies that ensure survival. To this end, escape behaviors must be adaptive. When a Drosophila melanogaster larva encounters a noxious stimulus, such as the focal pressure a parasitic wasp applies to the larval cuticle via its ovipositor, it initiates a characteristic escape response. The escape sequence consists of an initial abrupt bending, lateral rolling, and finally rapid crawling. Previous work has shown that the detection of noxious stimuli primarily relies on class IV multi-dendritic arborization neurons (Class IV neurons) located beneath the body wall, and more recent studies have identified several important components in the nociceptive neural circuitry involved in rolling. However, the neural mechanisms that underlie the rolling-escape sequence remain unclear. Here, we present both functional and anatomical evidence suggesting that bilateral descending neurons within the subesophageal zone of D. melanogaster larva play a crucial role in regulating the termination of rolling and subsequent transition to escape crawling. We demonstrate that these descending neurons (designated SeIN128) are inhibitory and receive inputs from a second-order interneuron upstream (Basin-2) and an ascending neuron downstream of Basin-2 (A00c). Together with optogenetic experiments showing that co-activation of SeIN128 neurons and Basin-2 influence the temporal dynamics of rolling, our findings collectively suggest that the ensemble of SeIN128, Basin-2, and A00c neurons forms a GABAergic feedback loop onto Basin-2, which inhibits rolling and thereby facilitates the shift to escape crawling.
The Enactment of Professional Boundary Work: A Case Study of Crime Investigation
Authors: Rantatalo Oscar , Lindberg Ola , Haake Ulrika
Published: January 2024

Professional boundary takes place as actors negotiate occupational boundaries and division of labour. In this article, we examine the conditions of defensive, accommodating, and configurational boundary work in the context of crime investigation. We analyse how professional boundaries are negotiated as civilian investigators become involved with policing. The article is based on 71 interviews with civilian and police crime investigators from a variety of investigation units in Sweden. Findings show how policing as a professional field is shifted as civilians from a wide variety of backgrounds and with varying motivations enter the occupation. Defensive boundary work that devalued civilians was widely occurring. However, boundary work that focused on learning, collaboration, and training was also occurring in high-status units. The discussion focuses on how power asymmetries impact boundary work when professions are undergoing change. This study exemplifies how organizational actors navigate, defend, and challenge their positions as professional boundaries are negotiated.
A domain-specific language for managing ETL processes
Authors: Popović Aleksandar , Ivković Vladimir , Trajković Nikola , Luković Ivan
Published: January 2024

Maintenance of Data Warehouse (DW) systems is a critical task because any downtime or data loss can have significant consequences on business applications. Existing DW maintenance solutions mostly rely on concrete technologies and tools that are dependent on: the platform on which the DW system was created; the specific data extraction, transformation, and loading (ETL) tool; and the database language the DW uses. Different languages for different versions of DW systems make organizing DW processes difficult, as minimal changes in the structure require major changes in the application code for managing ETL processes. This article proposes a domain-specific language (DSL) for ETL process management that mitigates these problems by centralizing all program logic, making it independent from a particular platform. This approach would simplify DW system maintenance. The platform-independent language proposed in this article also provides an easier way to create a unified environment to control DW processes, regardless of the language, environment, or ETL tool the DW uses.
Genome-wide association studies for earliness, MYMIV resistance, and other associated traits in mungbean (Vigna radiata L. Wilczek) using genotyping by sequencing approach
Authors: Kohli Manju , Bansal Hina , Mishra Gyan Prakash , Dikshit Harsh Kumar , Reddappa Shashidhar B. , Roy Anirban , Sinha Subodh Kumar , Shivaprasad K.M. , Kumari Nikki , Kumar Atul , Kumar Ranjeet R. , Nair Ramakrishnan Madhavan , Aski Muraleedhar
Published: January 2024

Yellow mosaic disease (YMD) remains a major constraint in mungbean (Vigna radiata (L.)) production; while short-duration genotypes offer multiple crop cycles per year and help in escaping terminal heat stress, especially during summer cultivation. A comprehensive genotyping by sequencing (GBS)-based genome-wide association studies (GWAS) analysis was conducted using 132 diverse mungbean genotypes for traits like flowering time, YMD resistance, soil plant analysis development (SPAD) value, trichome density, and leaf area. The frequency distribution revealed a wide range of values for all the traits. GBS studies identified 31,953 high-quality single nucleotide polymorphism (SNPs) across all 11 mungbean chromosomes and were used for GWAS. Structure analysis revealed the presence of two genetically distinct populations based on ΔK. The linkage disequilibrium (LD) varied throughout the chromosomes and at r2 = 0.2, the mean LD decay was estimated as 39.59 kb. Two statistical models, mixed linear model (MLM) and Bayesian-information and Linkage-disequilibrium Iteratively Nested Keyway (BLINK) identified 44 shared SNPs linked with various candidate genes. Notable candidate genes identified include FPA for flowering time (VRADI10G01470; chr. 10), TIR-NBS-LRR for mungbean yellow mosaic India virus (MYMIV) resistance (VRADI09G06940; chr. 9), E3 ubiquitin-protein ligase RIE1 for SPAD value (VRADI07G28100; chr. 11), WRKY family transcription factor for leaf area (VRADI03G06560; chr. 3), and LOB domain-containing protein 21 for trichomes (VRADI06G04290; chr. 6). In-silico validation of candidate genes was done through digital gene expression analysis using Arabidopsis orthologous (compared with Vigna radiata genome). The findings provided valuable insight for marker-assisted breeding aiming for the development of YMD-resistant and early-maturing mungbean varieties.
Regulación de la prohibición de fragmentación en la Ley N°19.886 de compras públicas
Authors:   , Navarrete Millon Matías
Published: January 2024

Realizar una investigación sobre la prohibición de fragmentar las contrataciones públicas con el propósito de variar el procedimiento de contratación, es necesario, puesto que hasta el día de hoy no ha recibido la atención suficiente por parte de los autores nacionales especializados en la materia, sin perjuicio de que el 10% de los informes de auditoría de la Contraloría General de la República que tocan temas relativos a compras públicas el año 2021 involucran situaciones de fragmentación, según información obtenida directamente desde el sistema de búsqueda de informes de dicho organismo de control. Así, esta investigación tendrá por objetivo contribuir a esclarecer cuando se está ante un caso de fragmentación, estando su primer capítulo enfocado en contextualizar la norma desde su génesis en nuestra regulación de compras públicas, un segundo capítulo enfocado en analizar el sentido de la prohibición, para continuar con el análisis pormenorizado de los elementos que componen la prohibición, es decir, cuando una contratación se entiende fragmentada, que procedimientos de compra se pueden variar y en que consiste el hecho de que la fragmentación se deba haber realizado con el propósito de variar el procedimiento de compra, un cuarto capítulo dedicado a los efectos de la fragmentación tanto respecto de las contrataciones fragmentadas como de los funcionarios involucrados en la comisión de los hechos y finalmente un capítulo dedicado el análisis de las formas de detección de estos casos a través del uso de los datos del sistema de información de las compras públicas. Este análisis se realizará, en parte, utilizando dictámenes e informes de auditoría de la Contraloría relativos a la materia, en cuanto principalmente es a través de estos mecanismos es que se ha dado contenido a la norma, esperando que las conclusiones obtenidas sirvan de guía a los funcionarios y servidores públicos que se dedican a la noble tarea de procurar abastecer a la Administración Pública de los suministros y servicios necesarios para el desarrollo de sus funciones.
β‐Cell Dysfunction in Type 2 Diabetes
Authors: Utzschneider Kristina M. , Kahn Steven E.
Published: November 2003

The pathogenesis of type 2 diabetes is complex, typically involving both insulin resistance and β‐cell dysfunction, with both defects being present well before the development of frank hyperglycemia and the clinical diagnosis of diabetes. This chapter reviews the abnormalities in β‐cell function observed in impaired glucose talerance and type 2 diabetes and elucidates some of the hypotheses regarding possible mechanisms responsible for the progressive failure of the β‐cell over time.
Switching
Authors: Freeman Roger L.
Published: November 2003

This chapter deals with the switching function of the PSTN. It is the general policy of telephone companies/administrations and the ITU not to dictate switch design to manufacturers. The ITU and Bellcore (now Telcordia) are, however, concerned with the digital network and its performance. A switch is an integral part of this network. For example, a switch provides master clock to outgoing trunks connected to it. A switch can degrade error performance. It adds to the total jitter and wander accumulation across the network. Queueing and processing delays can add to total end‐to‐end delay. Careful switch design can keep these impairments within reasonable bounds. Many of these
reasonable bounds
are established in the ITU
Q.500
recommendations and by Bellcore.

Switch interfacing is very important to the network designer. A local serving switch usually encounters analog subscriber loops (lines) on one side and digital trunks (junctions) on the other. Concentrators may or may not be used on the line side. This switch compresses and expands. In other words there will be more lines than trunks, with a ratio as high as 12 to 1 or as low as 1.5 to 1 depending on whether the traffic sources are predominantly residential or commercial/industrial. A switch will be designed for a grade‐of‐service 0.01, often to 0.005 or better. We would expect to encounter CCITT Signaling System No. 7 on the trunk side, and one of several types of subscriber loop signaling on the line side. The line side may utilize a DSL (digital subscriber line) which would appear as a multiplex configuration, often related to DS1 or E1. If a switch interfaces with ISDN basic rate, digital subscriber signaling will probably be used. There is a North American version and a CCITT version.

Tandem and transit exchanges do not provide compression and expansion. The number of trunk inlets will equal the number of trunk outlets. Tandem switches may provide a CAMA (centralized automatic message accounting) function. Modern tandem/transit exchanges use CCITT Signaling System No. 7.

Digital switch design is almost universally such that with small changes in peripheral equipment, the switch will serve either in an E1 or DS1 environment. The switch will consist of a switching fabric, peripheral equipment, and a processor/computer based control function. The switching fabric will often consist of time and space switching stages.
Numbering, Routing, and Networks
Authors: Freeman Roger L.
Published: November 2003

Nearly every telephone subscriber in the world can access every other subscriber. Such calls are routed over a vast international network based on direct/high‐usage routing and, in some cases, third country transit exchanges, connecting one or more international switching centers (ISCs) in each country. Each nation has its own national network that is a functional part of the international network. This chapter provides design data and standards material on those networks.

A telephone call is routed to its destination over the network [variably called the PSTN or public switched telecommunications (telephone) network] based on the telephone number provided by the calling subscriber. Thus, the first section of the chapter deals with numbering, the ITU‐T world numbering plan, and the North American plan. There is a brief section on international routing. This is followed by a section on the North American network and routing. Digital network management and quality of service (QoS) are briefly discussed.
Noise, Modulation, and Other Radio System Parameters
Authors: Freeman Roger L.
Published: November 2003

This chapter provides essential background material, basic data, and review of some key radio transmission parameters. Electrical noise is the key impairment in any transmission system. The chapter covers a basic treatise on thermal noise and includes discussions on intermodulation (IM) noise, frequency modulation (FM) noise, and phase noise. There is a short review of angle modulation, and a guide to the selection of digital modulation techniques for radio transmission is given emphasizing spectrum conservation. This is followed by a short discussion of four advanced digital modulation techniques such as block‐coded modulation, partial response with soft decision demodulator and trellis‐coded modulation. Information on the necessary bandwidth required for certain modulation techniques is covered; also discussed are ITU‐R (CCIR) views on radio frequency (RF), peak envelope, average and carrier power, and intermodulation products.
Multiplexing Techniques
Authors: Freeman Roger L.
Published: November 2003

Multiplexing facilitates the transmission of two or more information channels on a single transmission facility such as a wire pair, fiber‐optic strand, or radio carrier. Multiplexing can be either in the frequency domain or in the time domain. When in the frequency domain, it is called
frequency division multiplex
(FDM). When in the time domain, it is called
time division multiplex
(TDM).

FDM was the multiplexing technique of choice from before WWII to about 1985, when TDM systems became prevalent. At this juncture, nearly all multiplexing systems being implemented in the public switched telecommunication network (PSTN) use TDM.

For PSTN applications, the most prevalent type of TDM is called
pulse code modulation
(PCM).

As PCM systems evolved, two different underlying standards were developed. These may be typified by a North American standard popularly called T1 and by a European standard previously called CEPT30 + 2 and now popularly called E1. [CEPT stands for Conference European Post (and) Telegraph, a French‐dominated standards agency, now called ETSI (European Telecommunication Standardization Institute).] Both types of PCM standards are covered in chapter.

Because of the overwhelming dominance of PCM in the world's various networks, great emphasis has been placed on this multiplexing technique.
The Digital Network
Authors: Freeman Roger L.
Published: November 2003

The objective of this chapter is provide realizable performance objectives of the digital network as well as the impairments that can be expected and how to limit their impact on those performance objectives. The chapter also covers network synchronization without which that network would become inoperable or very badly degraded with excessive slips.

The
digital network
to which we refer is the underlying network supporting the PSTN. In industrialized countries the PSTN is completely digital; in emerging nations it is rapidly becoming so. The PSTN is a network open to public correspondence which supports the communication of voice, data, and video. There are also private and industrial networks. In many situations these private networks are backed up by the PSTN in case of dramatic failure or catastrophe. It is just for this reason we recommend private and industrial networks to follow PSTN practice (in most respects) so that there is a viable interface when the need arises. It is assumed that the digital network is based on 8‐bit PCM using either A‐law or μ‐law companding discussed earlier.

In North America there is not one singular network, but many networks under different ownerships. With the divestiture of the Bell System, seven regional Bell operating companies came into being. The long‐distance network consists of several or many competing carriers or IXCs depending on how one wishes to define a long‐distance carrier. Those with their own facilities with thousands of miles of transmission facilities and multiple switches may amount to six or seven, while others just resell service. The fact there are many interconnecting digital networks poses some difficult interfacing issues for the network designer, particularly multiple clock problems, where each of these networks has its own master clock.
Line‐of‐Sight Microwave
Authors: Freeman Roger L.
Published: November 2003

This chapter encompasses many of the basic design data elements for the planning, analysis, and implementation of line‐of‐sight microwave/millimeter wave radio‐links emphasizing point‐to‐point service.

Since 1975, the trend has been to implement digital line‐of‐sight (LOS) microwave because the world's networks either have become all‐digital or are rapidly becoming all digital. Because of the scarcity of available usable spectra, a particular burden has been placed on the microwave design engineer to conserve spectrum. Assuming a bit rate bandwidth, a digital voice channel occupies 64 kHz, whereas its analog counterpart would only use 4 kHz operating in a single sideband (SSB) mode. Thus, the system designer must turn to available bit packing techniques usually involving some sort of quadrature amplitude modulation (QAM) waveform. The 512‐QAM equipment is available with 1024‐QAM systems on the drawing boards providing 8 and 9 bits per hertz, respectively, of bit packing.

Line‐of‐sight microwave technology has two direct outgrowths: troposcatter/diffraction radiolinks and satellite communication systems. In fact, a communication satellite transponder is no more than a radiolink repeater or a regenerative repeater with possibly some additional signal processing. Another allied technology, mobile radio, covered under various terms such as cellular radio, personal communication services, or “wireless” communication, is also an extension of LOS microwave.
Meteor Burst Systems
Authors: Freeman Roger L.
Published: November 2003

Meteor burst communication (MBC) is a comparatively low‐cost, low‐throughput data communication system. A single MBC link can have a range up to about 1000 km. Data may only be passed when there is a common meteor trail visible by both the transmit and receive antennas. Such a trail may provide a viable path for periods up to 1 or 2 s.
The period between viable trails is called waiting time
. MBC links are commonly used for monitoring of remote sensors, where each sensor may be polled several times a day. MBC systems operate in the region around 50 MHz, which is a compromise between meteor trail activity and intensity versus man‐made noise.
Forward Error Correction
Authors: Freeman Roger L.
Published: November 2003

This chapter presents both tutorial information and practical design data on the application of forward error correction (FEC) techniques. FEC may only be used with digital circuits.

Forward error correction can be used to improve bit error performance on a marginal circuit or to lowerEb/N0requirements without impacting error performance on other digital circuits. The armed forces of the world were probably the first to put FEC to work. It now has universal acceptance in the commercial world. Where good bit error performance is crucial, one can expect to find FEC applied. This is particularly true on digital compression schemes such as motion picture experts group (MPEG). It is finding growing acceptance in the cellular/personal communication services (PCS) world and on line‐of‐sight (LOS) microwave and high‐frequency (HF) radio circuits.

Coding gainis defined as the difference between requiredEb/N0for an objective target bit error rate (BER) between a certain coded system and the same system without coding. A radio system “gain” is traditionally achieved by increasing transmitter power, improving receiver sensitivity, applying diversity, and increasing antenna aperture. Now on digital systems, coding gain derived from FEC is still another method to achieve gain, usually at a fairly reasonable price, by the addition of a personal computer (PC) board at each end of a link. Coding gains of 2–5 (or more) dB are common. To improve coding gain still further,tandem codingcan be employed. This is also called concatenated coding, where there is an inner code and an outer code. On one application, the outer code was a convolutional code with a coding gain of 5 dB, and the inner code was a Reed–Solomon block code with a coding gain of 2 dB. The net coding gain in this case was 7 dB.

Conventional wisdom agrees that the redundancy added for FEC requires an appropriate bandwidth expansion. When trellis‐coded modulation (TCM) is used, this is not the case. TCM is particularly attractive on digital LOS microwave circuits, where conservation of bandwidth is so important.
Facsimile Transmission
Authors: Freeman Roger L.
Published: November 2003

Facsimile (fax) is a method of electrical communication of graphic information. It is used to transmit pictorial or printed matter from one location to another with reasonably faithful copy recorded at the receiving end. Fax has been designed primarily to operate over comparatively narrow‐band media, lending itself to transmission over the telephone network on the standard 4‐kHz voice channel and on HF radio. Facsimile is transmitted in either (a) black and white or (b) black and white with various shades of gray. One system in operation has 256 shades of gray. Fax has truly become ubiquitous in many parts of the world.

This chapter is primarily concerned with facsimile interface data and standards, derived primarily from ITU‐T (CCITT) and US military documents. Another source is the US Electronic Industries Association (EIA). However, much of the EIA material is similar to ITU‐T Recommendations, and for that reason it has not been included.
Miscellaneous Data
Authors: Freeman Roger L.
Published: November 2003

This chapter contains general support information of interest to the telecommunication engineer. There is no direct relationship between this chapter and other chapters in the Reference Manual.
Adaptive Systems, Rotary Wing Applications
Authors: Chattopadhyay Aditi , Rajadas John
Published: November 2003

An intelligent or smart structure is generally considered an integrated system of structure, sensors, actuators, and a control module. Currently, there is a great deal of interest in applying smart structure technology to various physical systems. Active vibration, noise, aeroelastic stability, damping, shape control, health monitoring, process monitoring, and damage and delamination detection are a few examples. A significant amount of the early development was devoted to application to space‐related systems. Recently, studies have also been conducted to investigate using this concept to improve fixed wing performance. During the last decade, significant research efforts have also been directed toward applying these concepts to rotary wing aircraft which is the topic of this article. The potential for improving performance, handling qualities in stall, and increasing fatigue life is discussed. Actuators that use smart materials require relatively slow‐acting shape and shape‐distribution changes in this respect. A similar review is made of applications for improving aeroelastic divergence, flutter instabilities, and tail buffeting on fixed‐wing aircraft and reducing vibrations, improving external acoustics, and providing flight controls for rotary wing aircraft—all of these require a high‐frequency response.

Vibration and noise are two long‐standing problems that have limited the expansion of military and commercial applications of rotorcraft. Helicopters are particularly susceptible to high vibratory loads compared to fixed wing aircraft due to the high unsteady load and complex aerodynamic environment in which the rotor must operate and the existence of the complex structural, aerodynamic, and dynamic coupling.

A major improvement in helicopter performance can be achieved by implementing active rotor control technology. Smart material actuator technology for operation “on the blade” is now becoming available and promises to overcome the size, weight, and complexity of hydraulic and electric on‐rotor actuation which should alleviate the problem. Blade actuation by smart materials offers the chance for an electrical system integrated into the blade itself. Unfortunately, the development of high force/high deflection actuators, the most critical issue in all of these applications, has not been addressed adequately and still remains a topic of future research. In all applications involving smart materials, accurate modeling of the material response and the integrated smart structural response is important because control authority can be significantly mispredicted if inaccurate theories are used. In this article, the current state of the art in improving rotor vibratory response and aeromechanical characteristics is reviewed. Advantages and disadvantages of these techniques are discussed. Numerical results from feasibility studies are summarized, and accomplishments already achieved and the goals to be pursued in the near future are discussed.
Biomedical Applications
Authors: Qiu Jinhao , Tanaka Mami
Published: November 2003

Biomedical applications of smart materials can be divided into three categories: (1) implants and stents, such as bone plates and marrow needles; (2) surgical and dental instruments, devices, and fixtures, such as orthodontic fixtures and biopsy forceps; and (3) devices and instruments for medical checkups, such as ultrasonic devices. The applications of the first category require strict biocompatibility of a material because it is implanted in the body for long periods. Among many traditional materials, including metals, alloys, and ceramics, that are available commercially, only a limited number are currently used as prostheses or biomaterials in medicine and dentistry. The applications in the second category require excellent mechanical characteristics as well as biocompatibility. The third category is used mainly for transducers.

Among smart materials, the Ti–Ni shape‐memory alloy (SMA) has attracted the most attention for biomedical applications in the first and second categories due to its excellent biocompatibility and mechanical characteristics. Research on biomedical applications of the SMA started in the 1970s with animal experiments initially, followed by clinical tests. The first example of a successful biomedical application of the SMA was a bone plate, which was used to repair broken bones. Now, many medical and dental applications of SMAs are available, and many new applications are being developed. On the other hand, piezoelectric materials have been widely used as transducers for medical ultrasonic devices due to their sensor function that uses piezoelectricity and the actuator function that uses inverse piezoelectricity.

In this article, the properties of SMAs for biomedical applications are discussed next, followed by some clinical examples. Recent examples of biomedical applications of SMAs are summarized there after, and finally the recent examples of biomedical applications of piezoelectric materials are summarized.
Biomedical Sensing
Authors: Brazel Christopher S.
Published: November 2003

In recent years, biomedical diagnostics research has led to the development of simple, less invasive, and more accurate evaluative techniques. Much of this is due to biosensor technology, which has played an important role in material improvements used to sense, carry signals, and respond to signals. Biosensor devices can measure micromolar or even smaller quantities of biological substances, including chlorides, glucose, lactose, and urea. Medical applications abound, ranging from diagnostic tests for home testing toin vivomonitoring of vital conditions and using feedback to control drug delivery or send amplified signals of a change in patient health. Smart materials are frequently combined with biological components to create systems that respond to environmental conditions, such as temperature, pH, concentration of particular analytes, or even light. These smart materials are typically polymeric, and most have the common characteristic that changing environmental condition cause a thermodynamic change between hydrophilic and hydrophobic states, as detailed later. pH paper strips may be one of the simplest sensing devices; they relay a physiological condition through a colorimetric response, and because they are a form of dry chemistry, they simplify detection and diagnostics, which is especially important for home diagnostic kits.

This article presents the use of intelligent polymers in sensing systems, that range from traditional biosensors to advanced self‐responsive systems. This review of biomedical diagnostics using smart polymers examines some of the medical applications for intelligent polymers used in electrode‐based systems and in bioconjugate systems. Sensing devices are categorized by the mechanisms of signal detection and response, and examples of systems that monitor analytes, such as glucose, are addressed. Additional modes of response beyond the traditional electronic signal as well as synthesis techniques and examples of medical diagnostics using smart polymers, will be discussed.
Biosensors, Porous Silicon
Authors: Janshoff Andreas , Steinem Claudia
Published: November 2003

Biosensors consist of a biologically active layer that responding to an analyte in solution and a powerful transducer that transforms and amplifies the reaction into a measurable signal. Biosensors can constantly measure the presence, absence, or concentration of specific organic or inorganic substances in short response time and ultimately at low cost. They are used commercially in health care, biotechnological process control, agriculture, veterinary medicine, defense, and environmental pollution monitoring. A common requirement of all of these applications is on‐site chemical information—preferably in real time—on some dynamic or rapidly evolving process. Most biosensors are based on molecular events as they take place at the cellular membrane or inside the cell involving enzyme cascades. Their perceived advantages over existing technologies include the ability to monitor broad or narrow spectra of analytes continuously in real time, and their weakness is the instability of the biological molecules outside their natural environment, which results in a restricted lifetime for the device. The challenge is to find a matrix for biomolecules that provides high compatibility of the material with biological substances, low‐cost fabrication, and special optical and electrical properties to generate a signal that measures the interaction between analytes in solution and the receptive biological layer. It is also desirable that it be compatible with conventional microfabrication techniques to miniaturize the device or to build individually addressable arrays.

The high surface area in conjunction with its unique optical and electrical properties and its compatibility with silicon microelectronics fabrication techniques has led to the proposal that porous silicon may be a suitable material for building sensor devices. Several different transducer schemes have evolved based on thin film interference, capacitance changes, and the photoluminescent properties of porous silicon and these are discussed.
Ceramics, Transducers
Authors: Uchino Kenji , Ito Yukio
Published: November 2003

The various effects that relate the input—electric field, magnetic field, stress, heat and light—to the output—charge/current, magnetization, strain, temperature, and light are listed. Conducting and elastic materials that generate current and strain outputs, respectively, from input voltage, or stress are sometimes called “trivial” materials. Conversely, pyroelectric and piezoelectric materials that generate an electric field from the input of heat or stress are called “smart” materials. These off‐diagonal couplings have a corresponding converse effect such as electrocaloric and converse piezoelectric effects, and both “sensing” and “actuating” functions can be realized in the same materials. “Intelligent” materials should possess a “drive/control” or “processing” function which is adaptive to the change in environmental conditions, in addition to the actuation and sensing functions. Note that ferroelectric materials exhibit most of these effects, except magnetic‐related phenomena. Thus, the ferroelectrics are said to be very “smart” materials.

The “actuator” in a narrow meaning stands for materials or devices that generate mechanical strain (or stress) output. Solid state actuators use converse piezoelectric, magnetostriction, elasticity, thermal expansion, or photostriction phenomena. A shape‐memory alloy is a kind of thermally expanding material. On the other hand, a “sensor” requires charge/current output in most cases. Thus, conducting/semiconducting, magnetoelectric, piezoelectric, pyroelectric, and photovoltaic materials are used for detecting electric fields, magnetic fields, stress, heat, and light, respectively.

In this sense, piezoelectric materials are most popularly used in smart structures and systems because the same material is applicable to both sensors and actuators, in principle. In this article, we treat mainly piezoelectric transducers, sensors, and actuators. Although, transducers, in general, are devices that convert input energy to a different energy type of output, the piezoelectric “transducer” is often used to denote a device that possesses both sensing and actuating functions, exemplified by underwater sonar.
Characterization of Piezoelectric Ceramic Materials
Authors: Jordan T.L. , Ounaies Z.
Published: November 2003

This article explores piezoelectric ceramics analysis and characterization. The focus is on polycrystalline ceramics; therefore, single crystals, polymeric materials, and organic/inorganic composites are outside the scope of this article. To grasp the behavior of a piezoelectric polycrystalline ceramic thoroughly, a basic understanding of the ceramic itself should not be overlooked. To this end, we have presented a brief introduction of the history of piezoelectricity and a discussion on processing of the ceramic and the development of the constitutive relationships that define the behavior of a piezoelectric material. We have attempted to cover the most common measurement methods and to introduce parameters of interest. Excellent sources for more in‐depth coverage of specific topics can be found in the bibliography. In most cases, we refer to lead zirconate titanate (PZT) to illustrate some of the concepts because it is the most widely used and studied piezoelectric ceramic to date.
Coatings
Authors: Xu Chao‐Nan
Published: November 2003

Many materials emit light during the application of a mechanical energy. This phenomenon is usually referred to as mechanoluminescence (ML) or triboluminescence. The more historical term is “triboluminescence.” It stands for tribo‐induced luminescence, and this was the term used for more than a century to refer to light emission induced by any type of mechanical energy. The term “mechanoluminescence” was not proposed until 1978. The prefix “mechano” is correlated to the general mechanical way used for exciting luminescence, including concepts such as deformation, piezo, tribo, stress, cutting, grinding, rubbing, and fracto. In recent years mechanoluminescence (ML) has become the preferred nomenclature. Although the transfer of mechanical stress into light radiation is very complex, successes in experimental applications suggest possible uses of the ML phenomena in stress sensors, mechanical displays, and various smart systems.

In general, ML can be divided into fractoluminescence (destructive ML) and deformation luminescence (nondestructive ML); these correspond to the luminescence induced by fracture and mechanical deformation of solid, respectively. Roughly 50% of solid materials gives fractoluminescence by fracture: the well‐known materials include sugar, molecular crystals, alkali halides, quartz, silica glass, phosphors, piezoelectric complex, metals, various minerals, and biomaterials. Recently, the fractoluminescence of rare‐earth complexes was investigated in order to build smart damage sensors capable of simple real‐time detection of the magnitude and location of structural damage within materials. Deformation luminescence can be induced by mechanical deformation without fracture, and this is of interest in nondestructive evaluation. Deformation luminescence can be further divided into plasticoluminescence and elasticoluminescence. The former is produced during plastic deformation of solids, where fracture is not required, and the later is produced during the elastic deformation of solids where neither plastic deformation nor fracture is required. Nondestructive ML due to plastic deformation has been observed in several materials such as colored alkali halides, II–VI semiconductors, and rubbers. However, ML in the elastic region has been observed only for the irradiated alkali halides, and some piezoelectric materials. So far nondestructive luminescence intensities of materials have been reported to be too weak and difficult to repeat, and this has deferred any practical application of the phenomenon. For application of ML in developing new materials, repetitive ML must occur with undiminished intensity.
Chitosan‐Based Gels
Authors: De Yao Kang , Zhao Feng , Li Fang , Yin Yu Ji
Published: November 2003

Chitosan is a natural biopolymer obtained by deacetylation of chitin, which is produced from marine shellfish, such as crabs, shrimp, fungal cell wells, and other biological sources. Chemically it is a linear cationic poly(β‐(1‐4)‐2‐amino‐2‐deoxy‐D‐glucan) derived from chitin, a poly(β‐(1‐4)‐2‐acetamido‐2‐deoxy‐D‐glucan) by deacetylation. Chitosan is described in terms of the deacetylation degree and average molecular weight. And next to cellulose, it is the second most plentiful biomass and is already known as a biocompatible and biodegradable material. Many researchers have examined tissue response to various chitosan‐based implants. Results indicate that these materials evoke minimal foreign body reactions.

Gels consist of 3‐D polymer networks swollen in swellers, whereas hydrogels swell in water. Smart (intelligent) gels (or hydrogels) can swell or contract in response to stimulus changes, e.g., temperature, pH, ionic strength, chemicals, and fields.

Chitosan has been used for developing smart gels via network or/and complex formation. Due to their various properties that depend on environmental variables such as pH, ionic strength, and electric field, these materials have potential applications such as biomaterials, separation membranes, and field responsive materials.
Conductive Polymer Composites with Large Positive Temperature Coefficients
Authors: Wong C. P. , Luo Shijian
Published: November 2003

Conductive polymer composites that contain conductive fillers such as metal powder, carbon black, and other highly conductive particles in a nonconductive polymer matrix have been widely used in electrostatic dissipation (ESD) and electromagnetic interference shielding (EMIS). A special group among electrically conductive polymer composites are conductive polymer composites that have large positive temperature coefficients (PTC), which in some cases are called positive temperature coefficient resistance (PTCR). The resistivity of this kind of composite increases several orders of magnitude in a narrow temperature range. This kind of smart material can change from a conductive material to an insulating material or vice versa upon heating or cooling, respectively. The smartness of this kind material lies in this large PTC amplitude (defined as the ratio of maximum resistivity at the peak or the resistivity right after the sharp increase to the resistivity at 25°C), and also in its reversibility, its ability to adjustment the transition temperature, its low‐temperature resistivity, and high‐temperature resistivity. PTC behavior in a polymer composite was first discovered by Frydman in 1945, but not much attention was paid to it originally. Because Kohler obtained a much higher PTC amplitude from high density polyethylene loaded with carbon black in 1961, this kind of temperature‐sensitive materials has aroused wide research interest and also led to many very useful applications. In this article, the general theories of PTC conductive polymer are introduced. Carbon‐black‐filled conductive polymer composites and their PTC behavior are discussed in more detail, in regard to the effects of fillers, the polymer matrix, and processing conditions, and additives. Applications of this kind of smart temperature‐sensitive material are presented.