This means that its adaptive size prevents it from negatively impacting performance. Additionally, the thousands of read operations it satisfies enables Anticipatory Spin-Up functionality.These works generally conclude that a small non-volatile memory write-cache can significantly increase performance by reducing disk traffic. With hybrid disks soon to be available, hybrid disk/non-volatile memory file systems, such as Conquest and Hermes can be evaluated for their effectiveness at increasing file system performance by leveraging on-board non-volatile memory. Previous works have also looked at reducing hard disk power consumption using non-volatile memory. FLASH CACHE proposes to place a small amount of flash directly between main memory and disk, as an additional level in the caching hierarchy to decrease power-savings as well as increase performance. Nvcache focuses completely on reducing power management, and therefore has a completely different architecture. Although Anand et al. don’t use non-volatile memory, they propose ghost hints to anticipatively spin-up a hard disk in a mobile system context while redirecting read I/O to the Internet during disk spin-up. Microsoft proposes to use hybrid disk drives to reduce hard disk power consumption, and decrease boot-time and application launch in their upcoming Microsoft Vista Operating System. They claim a hybrid disk can be spundown by up to 96% of the time with a 1GB NVCache. Unfortunatelly, neither algorithms nor workloads are described. Duty cycle is only one metric for disk drive reliability. Disk drive reliability must also factor in duty hours, temperature, workload, and altitude. Mean Time To Failures and Mean Time Between Failures are widely used metrics to express disk drive reliability. However,black plastic pots for plants these metrics must considered with care, as they are often incorrect . IDEMA has proposed a revised MTBF rating based on disk age.
Most adaptive spin-down algorithms for traditional disks mention that disk reliability decreases when using a spin-down algorithm, but don’t quantitatively describe the impact. Greenawalt modeled the effects of different fixed time-out values and its impact on power conservation and disk reliability. They use a Poisson distribution to simulate inter-arrival access patterns and consider duty cycles as detracting X hours from the MTBF rating. Other strategies to save hard disk power involve pushing power management to applications. Weissel et al. propose that energy-aware interfaces should be provided to applications. Such interfaces can be used to convey priority or state information to an operating system. For example, deferrable I/O interfaces can be used by applications to in- form the operating system that particular I/O requests may be differed.The sediments of coastal marine wetlands in California are inhabited by a variety of algal and bacterial primary producers in addition to the more conspicuous vascular plants that provide most of the physical structure of coastal salt marshes and seagrass meadows. The non-vascular plant flora includes microscopic cyanobacteria, anoxygenic phototrophic bacteria, diatoms, and euglenoids, often collectively known as “microphytobenthos” . Larger green algae, red and brown seaweeds, and the macroscopic tribophyte, Vaucheria are also residents of these ecosystems . Ecologically, sediment-associated algae and photosynthetic bacteria are key components of wetland food webs . They account for a substantial fraction of ecosystem primary productivity in California and in other regions . While understanding of the ecological roles and spatio-temporal dynamics of these organisms has improved, the diversity and natural history of the micro- and macroalgae of salt marshes and mudflats from the northeastern Pacific, including southern California, are still poorly understood. Lack of a deeper understanding of the diversity of these organisms within and between estuaries and estuarine habitat types impedes efforts to understand how spatio-temporal variation in the composition of benthic assemblages may affect ecosystem functions or how changes in assemblages may relate to anthropogenic impacts to wetlands.
To date no comprehensive floristic account of wetland algae and photosynthetic bacteria in California has been produced by the phycological community. However, some taxonomic information on these organisms exists in scattered sources. Early research on the taxonomy of wetland algae began with William Setchell, Nathaniel Gardner, and George Hollenberg. These phycologists produced lists and/or descriptions of cyanobacteria and macroalgae from salt marshes and mudflats in several publications, but the accounts principally focused on either rocky shore cyanobacteria or wetland vascular plant floras . Several decades later, Zedler published a list of cyanobacteria, diatoms, and green algae collected from Tijuana Estuary at the southern extreme of the state. She recorded 32 species of diatoms, four cyanobacterial taxa, and the green algal genera Rhizoclonium and Enteromorpha, but noted that her account was not comprehensive. Wilson and Carpelan studied benthic diatoms from Mugu Lagoon and pelagic diatoms in four lagoons in northern San Diego County respectively. Records of wetland macroalgae have been compiled for Humboldt Bay in northern California , and for Newport Bay in southern California. Stewart’s treatment of San Diego County seaweeds also notes wetland occurrences of marine macroalgae. There are formidable obstacles to producing a comprehensive flora of tidal wetland algae for any localized region. First, the phylogenetic breadth of photosynthetic organisms in tidal wetland habitats requires a diversity of specialists, employing an array of tools from electron microscopy to culturing techniques to standard phycological methods for macroalgal identification and preservation. As Sullivan and Currin note, funding for such an endeavor is likely to be difficult to acquire. Moreover, the systematics of many groups of these organisms is in flux. In particular, study of the cyanobacteria is complicated by the existence of competing bacteriological and morphological classification schemes and by widely differing approaches to using morphology to delineate species . An additional consideration is that application of names to microalgal and cyanobacterial taxa for a given locality is at least somewhat dependent on decisions made in other geographic regions or habitats since detailed taxonomic studies are haphazardly distributed in space and time.
For instance, some important cyanobacterial reference sources either treat distant geographic areas or describe primarily freshwater and terrestrial organisms . Despite these challenges, floristic and systematic work on wetland microalgae and seaweeds provides the foundation for progress in basic biodiversity research. In addition to the possibility that cryptic taxa may be discovered in the flora, algae are excellent systems for investigation of molecular versus morphologically-based phylogenies . Better knowledge of the diversity of microproducers present in coastal wetland habitats should also enable a better understanding of ecological interactions between microphytobenthos and other wetland organisms and facilitate the use of biodiversity metrics as a means of assessing ecosystem health and dynamics. In this paper the common benthic cyanobacteria, microalgae, and seaweeds associated with sediments from tidal wetlands in southern California are described and illustrated. The goal is to provide preliminary documentation of the local flora and add to the fragmentary knowledge of these organisms in the region. The paper focuses on new collections made from Mission Bay and Tijuana Estuary in San Diego County,drainage pot but also includes some records of species previously recorded from wetlands throughout southern California . Organisms included here were assigned tentative genus names based on morphological features visible by eye or by light microscopy. Supporting references pertinent to the identification of taxa, their local distribution, and their natural history, are also included. Of the various taxa treated, documentation of the cyanobacteria is most thorough, partly filling the significant gap in information on these common inhabitants of tidal wetlands in the region. Observations and photographic documentation were made on live organisms, or occasionally on organisms grown in culture. Specimens were often kept alive by transferring moist field sediment to incubation in the laboratory. Field sediment and cultures were maintained at about room temperature with illumination . Cultured organisms were grown on sterilized f/2 media prepared in artificial seawater with or without sterilized glass particles as a substrate. Organisms living on field-collected sediment were kept and observed up to about seven months following removal from the field . Photographs were taken with a digital camera through compound microscopes . Diatoms were identified to genus where possible using Round et al. . Cyanobacterial taxa were generally identified to genus using the recent taxonomic treatments in Anagnostidis and Komárek , Komárek and Anagnostidis , and Boone and Castenholz . Humm and Wicks , Desikachary , and Setchell and Gardner were also consulted for identification and nomenclatural purposes. Macroalgae attached to sediment-associated substrates or occurring loosely in wetland habitats were pressed fresh on herbarium paper and dried. Identification and current nomenclature of macroalgae follows Abbott and Hollenberg and Gabrielson et al. . Skin is one of the largest organs of the body and has functional roles in immune response, physical protection, and thermal regulation. As aging occurs, skin function and healing capacity is reduced. Skin aging is frequently divided into two related processes: intrinsic and extrinsic aging . Intrinsic aging, also referred to as chronological aging, includes genetic and hormonal changes and the progression from cell maturity to cellular senescence. Extrinsic aging, also referred to as environmental aging, represents the impact of the environment, including: photo aging associated with sun exposure , cigarette smoking, pollution, chemical exposure, trauma. Due to the different underlying mechanisms, characteristics of each type of aged skin are different. Chronologically aged skin presents as unblemished, smooth, pale, dry, lower elasticity, and has fine wrinkles while environmentally aged skin has coarse wrinkling, rough textures, pigmentation changes, and lower elasticity.
Microstructural changes in intrinsically aged skin include decreased dermal vasculature ; changes in dermal elasticity and increased collagen disorganization; build-up of advanced glycation end products and changes in glycosaminoglycan and proteoglycan concentrations/organization contributing to stiffening of dermal structure and frailty, and decreased hydration; imbalance of tissue inhibitors and matrix metalloproteinases resulting in imbalance between collagen deposition and breakdown; and flattening of the dermal epidermal junction/loss of rete ridges. Aging also contributes to variations in epidermal and dermal thickness and reduced subcutaneous fat volume. There are also many changes related to cell population in all three main skin compartments including reduced epidermal cell turnover, drop in number of active melanocytes ; decreases in dermal fibroblast concentrations, decreases in immune cells and immune function. Abnormalities of skin barrier occur during aging and often present as dryness or skin irritation. In aged skin, barrier function has been studied in the context of decreases of filaggrin, increases in pH , altered lipid presence, and changes in cornified envelope arrangement. These changes add to fragility of older skin and higher chances of infection, it remains unclear exactly how these changes take place and what mechanisms are controlling them. On the molecular scale, expression levels of soluble factors, proteins, and vitamins are both effects and contributors to aging phenotypes. Examples include upregulation of stress regulatory proteins, increases in AP-1, and declines in vitamin D production by the epidermis. These changes are largely attributed to increases in reactive oxygen species, DNA mutations , telomere shortening, increased cell senescence, and hormonal changes. Changes in skin aging have been associated with fluctuations in expression patterns of integrins including α6 and ß1 integrins.In healthy human skin, α6 and ß1 integrin expression are localized on the basal side of basal keratinocytes. Defects in integrin expression are present in human blistering skin diseases with supporting evidence in knockout mice 34 and also in aged human skin ,although further work is necessary to understand how integrin expression changes in aging. Aging in the skin has sex-related differences as well, specifically, sex is linked to faster thinning of the dermis and collagen density decline in males as opposed to females. Males undergo a decline in androgen levels while estradiol levels are constant, these changes result in a linear decline of skin thinning and collagen content in men 10. Women experience both androgen and estrogen decline linearly and an additional post-menopausal estrogen decline which is linked to lower collagen content, lower skin moisture and capacity to hold water, lessened would healing response, thinner skin, and lower skin elasticity. Detailed summary and discussion of sex-related changes in skin aging have been previously reviewed. These intrinsic mechanisms are compounded by environmental skin aging . A key example is the effects of ultraviolet irradiation , which accelerates telomere shortening and DNA damage present with intrinsic aging. Other extrinsic aging and examples of compounding UV effects are discussed in previous literature. Overall, skin aging at the molecular, cellular, and tissue levels continues to be a field of active research.