Dietary 14C reservoir effects and the chronology of prehistoric burials at Sakhtysh, central European Russia

We present a robust radiocarbon (14C) chronology for burials at Sakhtysh, in European Russia, where nearly 180 inhumations of Lyalovo and Volosovo pottery-using hunter-gatherer-fishers represent the largest known populations of both groups. Past dating attempts were restricted by poor understanding of dietary 14C reservoir effects (DREs). We developed a DRE correction approach that uses multiple linear regression of differences in 14C, δ13C, and δ15N between bones and teeth of the same individuals to predict DREs of up to approximately 900 years. Our chronological model dates Lyalovo burials to the early fifth millennium BCE, and Volosovo burials to the mid-fourth to early third millennium. It reveals a change in the subsistence economy at approximately 3300 BCE, coinciding with a reorientation of trade networks, and dates the final burial to the early Fatyanovo period, the regional expression of the Yamnaya/Corded Ware expansion. Our approach is applicable when freshwater 14C reservoir effects are poorly constrained and grave goods cannot be dated directly.

The impact of farming on prehistoric culinary practices throughout Northern Europe

To investigate changes in culinary practices associated with the arrival of farming, we analysed the organic residues of over 1,000 pottery vessels from hunter-gatherer-fisher and early agricultural sites across Northern Europe from the Lower Rhine Basin to the Northeastern Baltic. Here, pottery was widely used by hunter-gatherer-fishers prior to the introduction of domesticated animals and plants. Overall, there was surprising continuity in the way that hunter-gatherer-fishers and farmers used pottery. Both aquatic products and wild plants remained prevalent, a pattern repeated consistently across the study area. We argue that the rapid adaptation of farming communities to exploit coastal and lagoonal resources facilitated their northerly expansion, and in some cases, hunting, gathering, and fishing became the most dominant subsistence strategy. Nevertheless, dairy products frequently appear in pottery associated with the earliest farming groups often mixed with wild plants and fish. Interestingly, we also find compelling evidence of dairy products in hunter-gatherer-fisher Ertebølle pottery, which predates the arrival of domesticated animals. We propose that Ertebølle hunter-gatherer-fishers frequently acquired dairy products through exchange with adjacent farming communities prior to the transition. The continuity observed in pottery use across the transition to farming contrasts with the analysis of human remains which shows substantial demographic change through ancient DNA and, in some cases, a reduction in marine consumption through stable isotope analysis. We postulate that farmers acquired the knowledge and skills they needed to succeed from local hunter-gatherer-fishers but without substantial admixture.

Finite element analysis of biomechanical interactions of a subcutaneous suspension suture and human face soft-tissue: a cadaver study

In order to study the local interactions between facial soft-tissues and a Silhouette Soft® suspension suture, a CE marked medical device designed for the repositioning of soft tissues in the face and the neck, Finite element simulations were run, in which a model of the suture was embedded in a three-layer Finite Element structure that accounts for the local mechanical organization of human facial soft tissues. A 2D axisymmetric model of the local interactions was designed in ANSYS, in which the geometry of the tissue, the boundary conditions and the applied loadings were considered to locally mimic those of human face soft tissue constrained by the suture in facial tissue repositioning. The Silhouette Soft suture is composed of a knotted thread and sliding cones that are anchored in the tissue. Hence, simulating these interactions requires special attention for an accurate modelling of contact mechanics. As tissue is modelled as a hyper-elastic material, the displacement of the facial soft tissue changes in a nonlinear way with the intensity of stress induced by the suture and the number of the cones. Our simulations show that for a 4-cone suture a displacement of 4.35 mm for a 2.0 N external loading and of 7.6 mm for 4.0 N. Increasing the number of cones led to the decrease in the equivalent local strain (around 20%) and stress (around 60%) applied to the tissue. The simulated displacements are in general agreement with experimental observations.

Indigenous forest livelihoods and bauxite mining: A case-study from northern Australia

Bauxite mining operations are increasingly sited on Indigenous-owned land, particularly in tropical areas, including northern Australia. The environmental impacts of bauxite mining are significant. Native vegetation, including commercially valuable forests, is cleared and typically windrowed and burnt. For many Indigenous Australians, mining of their land creates much concern about biocultural, community health and livelihood impacts from the loss of access to traditional lands and resources, and the ability to 'care for country'. Improved pre-mining utilisation of forest resources and effective mine rehabilitation can mitigate some of these impacts and it is important to Indigenous communities that they are engaged in these processes. But Indigenous peoples' expectations are rarely considered or adequately addressed in site clearing activities or mine completion criteria, and there is limited guidance on how their expected outcomes can be monitored and evaluated for mine closure and relinquishment. This paper reports on a case-study of the Western Cape York Peninsula bauxite mining region in northern Australia. The paper reviews mine rehabilitation in the case-study region, including related Indigenous forest livelihoods initiatives, presents local Indigenous peoples' expectations for pre- and post-mining forest and landscape management as an integrated mining-community forestry 'vision', and discusses implications for mine completion criteria, mine closure and relinquishment. The findings highlight the need for Indigenous peoples' full and transparent free, prior and informed consent participation in all aspects of mine closure planning, and for further research to trial the development and assessment of mine completion criteria linked to local biocultural landscape restoration and Indigenous livelihoods. The findings can inform mining policymakers, regulators and industry professionals on the design, implementation and monitoring of mine completion criteria and associated pre- and post-mining management that will improve environmental outcomes and socio-cultural benefits for Indigenous communities impacted by mining.

Neolithic farmers or Neolithic foragers? Organic residue analysis of early pottery from Rakushechny Yar on the Lower Don (Russia)

The emergence of pottery in Europe is associated with two distinct traditions: hunter-gatherers in the east of the continent during the early 6th millennium BC and early agricultural communities in the south-west in the late 7th millennium BC. Here we investigate the function of pottery from the site of Rakushechny Yar, located at the Southern fringe of Eastern Europe, in this putative contact zone between these two economic 'worlds'. To investigate, organic residue analysis was conducted on 120 samples from the Early Neolithic phase (ca. mid-6^th millennium BC) along with microscopic and SEM analysis of associated foodcrusts. The results showed that the earliest phase of pottery use was predominantly used to process riverine resources. Many of the vessels have molecular and isotopic characteristics consistent with migratory fish, such as sturgeon, confirmed by the identification of sturgeon bony structures embedded in the charred surface deposits. There was no evidence of dairy products in any of the vessels, despite the fact these have been routinely identified in coeval sites to the south. Further analysis of some of the mammalian bones using ZooMS failed to demonstrate that domesticated animals were present in the Early Neolithic. Nevertheless, we argue that intensive exploitation of seasonally migratory fish, accompanied by large-scale pottery production, created storable surpluses that led to similar socio-economic outcomes as documented in early agricultural societies.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12520-021-01412-2.

A 5,000-year-old hunter-gatherer already plagued by Yersinia pestis

A 5,000-year-old Yersinia pestis genome (RV 2039) is reconstructed from a hunter-fisher-gatherer (5300-5050 cal BP) buried at Riņņukalns, Latvia. RV 2039 is the first in a series of ancient strains that evolved shortly after the split of Y. pestis from its antecessor Y. pseudotuberculosis ∼7,000 years ago. The genomic and phylogenetic characteristics of RV 2039 are consistent with the hypothesis that this very early Y. pestis form was most likely less transmissible and maybe even less virulent than later strains. Our data do not support the scenario of a prehistoric pneumonic plague pandemic, as suggested previously for the Neolithic decline. The geographical and temporal distribution of the few prehistoric Y. pestis cases reported so far is more in agreement with single zoonotic events.

Genome-wide study of a Neolithic Wartberg grave community reveals distinct HLA variation and hunter-gatherer ancestry

The Wartberg culture (WBC, 3500-2800 BCE) dates to the Late Neolithic period, a time of important demographic and cultural transformations in western Europe. We performed genome-wide analyses of 42 individuals who were interred in a WBC collective burial in Niedertiefenbach, Germany (3300-3200 cal. BCE). The results showed that the farming population of Niedertiefenbach carried a surprisingly large hunter-gatherer ancestry component (34–58%). This component was most likely introduced during the cultural transformation that led to the WBC. In addition, the Niedertiefenbach individuals exhibited a distinct human leukocyte antigen gene pool, possibly reflecting an immune response that was geared towards detecting viral infections.

Alexander Immel et al. performed genome-wide analyses of 42 individuals from a collective burial in Niedertiefenbach, Germany from the Wartberg Culture. The authors find that this population had a large hunter-gatherer ancestry component and a distinct HLA pool, which indicates immune defenses against viral pathogens.

New AMS 14C dates track the arrival and spread of broomcorn millet cultivation and agricultural change in prehistoric Europe

Broomcorn millet (Panicum miliaceum L.) is not one of the founder crops domesticated in Southwest Asia in the early Holocene, but was domesticated in northeast China by 6000 BC. In Europe, millet was reported in Early Neolithic contexts formed by 6000 BC, but recent radiocarbon dating of a dozen 'early' grains cast doubt on these claims. Archaeobotanical evidence reveals that millet was common in Europe from the 2nd millennium BC, when major societal and economic transformations took place in the Bronze Age. We conducted an extensive programme of AMS-dating of charred broomcorn millet grains from 75 prehistoric sites in Europe. Our Bayesian model reveals that millet cultivation began in Europe at the earliest during the sixteenth century BC, and spread rapidly during the fifteenth/fourteenth centuries BC. Broomcorn millet succeeds in exceptionally wide range of growing conditions and completes its lifecycle in less than three summer months. Offering an additional harvest and thus surplus food/fodder, it likely was a transformative innovation in European prehistoric agriculture previously based mainly on (winter) cropping of wheat and barley. We provide a new, high-resolution chronological framework for this key agricultural development that likely contributed to far-reaching changes in lifestyle in late 2nd millennium BC Europe.

Correction to 'Organic residue analysis shows sub-regional patterns in the use of pottery by Northern European hunter-gatherers'

[This corrects the article DOI: 10.1098/rsos.192016.].

Organic residue analysis shows sub-regional patterns in the use of pottery by Northern European hunter-gatherers

The introduction of pottery vessels to Europe has long been seen as closely linked with the spread of agriculture and pastoralism from the Near East. The adoption of pottery technology by hunter-gatherers in Northern and Eastern Europe does not fit this paradigm, and its role within these communities is so far unresolved. To investigate the motivations for hunter-gatherer pottery use, here, we present the systematic analysis of the contents of 528 early vessels from the Baltic Sea region, mostly dating to the late 6th-5th millennium cal BC, using molecular and isotopic characterization techniques. The results demonstrate clear sub-regional trends in the use of ceramics by hunter-gatherers; aquatic resources in the Eastern Baltic, non-ruminant animal fats in the Southeastern Baltic, and a more variable use, including ruminant animal products, in the Western Baltic, potentially including dairy. We found surprisingly little evidence for the use of ceramics for non-culinary activities, such as the production of resins. We attribute the emergence of these sub-regional cuisines to the diffusion of new culinary ideas afforded by the adoption of pottery, e.g. cooking and combining foods, but culturally contextualized and influenced by traditional practices.

Highly stretchable hydrogels from complex coacervation of natural polyelectrolytes

The controlled complex coacervation of oppositely charged hyaluronic acid (M_w ≈ 800-1000 kg mol^-1) and chitosan (M_w ≈ 160 kg mol^-1, degree of acetylation = 15%) led to hydrogels with controllable properties in terms of elasticity and strength. In this work, we performed desalting by dialysis of high ionic strength solutions of mixed polyelectrolytes and showed that the control of the pH during the polyelectrolyte assembly greatly impacts the mechanical properties of the hydrogel. First, for pHs from 5.5 to 7.5, a slight coacervation was observed due to low chitosan protonation and poor polyelectrolyte associations. Then, for pHs from 3.0 to 5.5, coacervation and syneresis led to free-standing and easy to handle hydrogels. Finally, for pHs from 2.0 to 3.0 (close to the pK_a of the hyaluronic acid), we observed the unusual stretchability of these hydrogels that could arise from the pre-folding of hyaluronic acid chains while physical crosslinking was achieved by hyaluronic acid/chitosan polyelectrolyte complexation.

Severe left diaphragmatic hernia limits size of fetal left heart more than does right diaphragmatic hernia

OBJECTIVES

To assess whether severity of congenital diaphragmatic hernia (CDH) correlates with the degree of left heart hypoplasia and left ventricle (LV) output, and to determine if factors leading to abnormal fetal hemodynamics, such as compression and reduced LV preload, contribute to left heart hypoplasia.

METHODS

This was a retrospective cross-sectional study of fetuses at 16-37 weeks' gestation that were diagnosed with CDH between 2000 and 2010. Lung-to-head ratio (LHR), liver position and side of the hernia were determined from stored ultrasound images. CDH severity was dichotomized based on LHR and liver position. The dimensions of mitral (MV) and aortic (AV) valves and LV were measured, and right and left ventricular outputs were recorded.

RESULTS

In total, 188 fetuses with CDH were included in the study, 171 with left CDH and 17 with right CDH. Fetuses with severe left CDH had a smaller MV (Z = -2.24 ± 1.3 vs -1.33 ± 1.08), AV (Z = -1.39 ± 1.21 vs -0.51 ± 1.05) and LV volume (Z = -4.23 ± -2.71 vs -2.08 ± 3.15) and had lower LV output (26 ± 10% vs 32 ± 10%) than those with mild CDH. MV and AV in fetuses with right CDH (MV, Z = -0.83 ± 1.19 and AV, Z = -0.71 ± 1.07) were larger than those in fetuses with left CDH, but LV outputs were similarly diminished, regardless of hernia side. Severe dextroposition and abnormal liver position were associated independently with smaller left heart, while LHR was not.

CONCLUSION

The severity of left heart hypoplasia correlates with the severity of CDH. Altered fetal hemodynamics, leading to decreased LV output, occurs in both right- and left-sided CDH, but the additional compressive effect on the left heart is seen only when the hernia is left-sided. Improved knowledge of the physiology of this disease may lead to advances in therapy and better risk assessment for use in counseling affected families.

Review and follow-up of patients using a regional sperm cryopreservation service: ensuring that resources are targeted to those patients most in need

Are all patients undergoing chemotherapy for long-term sperm banking at risk of permanent sterility? Male fertility is generally lower in men with cancer and all patient groups are at risk of azoospermia. Careful management is required to ensure that samples are not stored for excessively long periods should they not be required. A retrospective analysis of 1688 patient records and prospective recall of patients for semen testing were performed. Pre-therapy fertility was compared with a group of pre-vasectomy patients as a comparator. Those who fail to bank spermatozoa, rates of disposal of samples and the utilization in assisted reproduction were also examined. Sperm quality was poorest in testicular cancer (TC) patients followed by those with Hodgkin's lymphoma (HL) prior to treatment. Post-therapy data were available in 376 patients (42%). Sperm number was lowest (and azoospermia highest at 77%) in patients with HL treated with regimens other than adriamycin, bleomycin, vinblastine and dacarbazine (ABVD). Non-HL NHL and leukaemic patients had similarly high rates of azoospermia at 46 and 55%. HL patients treated with ABVD (11%) and TC patients (9.7%) had the lowest rates of azoospermia. Azoospermia was seen in every treatment group except for TC patients receiving carboplatin. Only 45 patients used their samples in ART (4.5%) in 10 years. Little is known about the fertility status of the patients not coming forward for follow-up testing, those conceiving naturally, those with no intention of conceiving and some which may have psychological reasons for not attending. In conclusion, virtually all patients undergoing chemotherapy are potentially at risk of temporary or permanent infertility. However, as uptake and utilization of stored material remain low, sperm banks should be carefully managed to ensure that resources are targeted to the patients most in need.

Physicochemical Characterization of Konjac Glucomannan

Four commercial konjac glucomannan (KGM) samples and a glucomannan derived from yeast were characterized by aqueous gel permeation chromatography coupled with multi angle laser light scattering (GPC-MALLS). Disaggregation of aqueous glucomannan solutions through controlled use of a microwave bomb facilitated reproducible molar mass distribution determination alleviating the need for derivatization of the polymer or the use of aggressive solvents. Further characterization was undertaken by use of capillary viscometry and photon correlation spectroscopy (PCS). The weight average molecular masses (M(w)) determined were in the region of 9.0 +/- 1.0 x 10(5) g mol(-1) for KGM samples and 1.3 +/- 0.4 x 10(5) g mol(-1) for the yeast glucomannan. The values determined for KGM in aqueous solution are in agreement with those reported for KGM in aqueous cadoxen. The degradation of samples observed upon autoclaving has been quantified by GPC-MALLS and intrinsic viscosity determination, allowing comparison with reported Mark-Houwink parameters. Shear flow experiments were undertaken for a range of KGM solutions of concentration 0.05 to 2.0% using a combination of controlled stress and controlled strain rheometers. The concentration dependence of the zero shear specific viscosity was determined by analysis of the data using the Ellis model. The dependence of the zero shear specific viscosity on the coil overlap parameter was defined and interpretation discussed in terms of the Martin and Tuinier equations.

The molecular diversity of the methanogenic community in a hypereutrophic freshwater lake determined by PCR-RFLP

AIMS

To combine database-held sequence information with a programme of experimental molecular ecology to define the methanogenic community of a hypereutrophic lake by a PCR-restriction fragment length polymorphism (RFLP) analysis.

METHODS AND RESULTS

Methanogen diversity in a hypereutrophic freshwater lake was analysed using 16S rDNA PCR-RFLP. Database-held 16S rRNA gene sequences for 76 diverse methanogens were analysed for specific restriction sites that permitted unequivocal differentiation of methanogens. Restriction digestion and agarose gel electrophoresis of the 16S rDNA from selected methanogen pure cultures generated observed restriction profiles that corroborated the expected patterns. This method was then tested by analysing methanogen diversity in samples obtained over 1 year from sediment and water samples taken from the same sampling site.

CONCLUSIONS

Restriction analysis of the 16S rRNA gene sequences from 157 methanogen clones generated from lakewater and sediment samples showed that over 50% were similar to Methanoculleus spp. Furthermore, a total of 16 RFLP types (1-16) were identified, eight of which contained no cultured representative archaeal 16S rRNA gene sequences.

SIGNIFICANCE AND IMPACT OF THE STUDY

This RFLP strategy provides a robust and reliable means to rapidly identify methanogens in the environment.

Toxicity of o,p'-DDE to medaka d-rR strain after a one-time embryonic exposure by in ovo nanoinjection: an early through juvenile life cycle assessment

The toxicity of o,p'-DDE (1,1-dichloro-2-(p-chlorophenyl)-2-(o-chlorophenyl) ethylene) was evaluated in embryos of medaka (Oryzias latipes) following a one time exposure via nanoinjection. Medaka eggs (early gastrula) were injected with 0.5 nl of triolein (vehicle control) or 0.5 nl of 4 graded doses (0.0005-0.5 ng/egg) of o,p'-DDE in triolein. Embryos were allowed to develop, and fry were reared. Embryonic survival was monitored daily during the first 10 d until hatching and thereafter, on a weekly basis until day 59, at which time the fish were monitored for sexual maturity until day 107. In general, o,p'-DDE caused a dose- and time-dependent mortality. No changes in mortality were observed between the last two time points (day 38 and 59, respectively), and hence a 59 day-LD50 of 346 ng o,p'-DDE/egg was derived from the linear dose-response relationship. Prior to late stage death, only isolated cases of cardiovascular lesions and spinal deformities were observed, but were not dose-dependent. The lowest observable adverse effect level (LOAEL), based on upper 95% CI for regression line=0.0018 mg/kg, and the LOAEL based on exposure doses=0.5 mg/kg. Likewise, the no observable adverse effect level (NOAEL) based on linear extrapolation to 100% survival=0.0000388 mg/kg, while the NOAEL based on exposure doses=0.05 mg/kg. The nanoinjection medaka model has potential in the study of hormonally active compounds in the environment.

In ovo exposure to o,p -DDE affects sexual development but not sexual differentiation in Japanese medaka (Oryzias latipes)

Despite being banned in many countries, dichlorodiphenyltrichloroethane (DDT) and its metabolites dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD) continue to be found in fish tissues at concentrations of concern. Like o,p -DDT, o,p -DDE is estrogenic and is believed to exert its effects through binding to the estrogen receptor. The limited toxicologic data for o,p -DDE suggest that it decreases fecundity and fertility of fishes. We conducted an egg injection study using the d-rR strain of medaka and environmentally relevant concentrations of o,p -DDE to examine its effects on sexual differentiation and development. The gonads of exposed fish showed no evidence of sex reversal or intersex. However, other gonad abnormalities occurred in exposed individuals. Females exhibited few vitellogenic oocytes and increased atresia. Male testes appeared morphologically normal but were very small. Gonadosomatic index values for both sexes were lower for exposed fish. Our observations of abnormal female and very small male gonads after in ovo o,p -DDE exposure may be indicative of effects on early endocrine processes important for normal ovarian and testicular development.

Determining the molar mass of a plasma substitute succinylated gelatin by size exclusion chromatography-multi-angle laser light scattering, sedimentation equilibrium and conventional size exclusion chromatography

The clinical effectiveness of succinylated gelatin as a plasma substitute depends strongly on its molar mass, determined conventionally by size exclusion chromatography (SEC). This study evaluates different SEC calibration standards in comparison with two independent "absolute" methods for determining the weight average molar mass (M(w)) of a succinylated gelatin sample. SEC calibrated using succinylated gelatin fractions correlated well with size exclusion chromatography-multi-angle laser light scattering (SEC-MALLS) and sedimentation equilibrium whereas SEC calibrated with unmodified gelatin, sodium polystyrene sulfonates or pullulans overestimated M(w) by over 20%. Universal calibration was equivocal. The problems associated with the preparation of succinylated gelatin fractions suggest that an absolute method such as SEC-MALLS may be a more suitable choice for determining the M(w) in succinylated gelatins.

Solution rheology of kappa-carrageenan in the ordered and disordered conformations

The order-disorder conformational transition of kappa-carrageenan, induced by both electrolyte and temperature, was found to give rise to significantly different rheological properties under shear flow, extensional flow, and small deformation oscillation regimes. Shear flow displayed only shear thinning or Newtonian behavior, depending of the chain conformation. A larger range of properties was observed in elongational flow. Strain-thinning behavior was observed in the ordered conformation while strain thickening occurred in the disordered conformation. These results are discussed as a function of the chain conformation.

A rheological study of the order-disorder conformational transition of xanthan gum

The rheological properties of a moderately concentrated solution of xanthan gum in both the ordered and the disordered state have been studied. Oscillatory shear, steady shear flow, and extensional flow experiments have been performed at different temperatures, covering the order-disorder transition determined by differential scanning calorimetry (DSC). The principle of time/temperature superposition was applied to the xanthan solutions for the different types of flow. Although a master curve covering six decades of frequency could be obtained for the storage modulus over the entire investigated temperature range, less agreement was found for the other modulus. This indicates that the order-disorder transition reflects changes on the molecular scale and slight modification of the physical network structure. To the authors' knowledge, this is the first time that this transition has been observed using these different rheological techniques.

Are we meeting the psychological needs of Black African HIV-positive individuals in London? Controlled study of referrals to a psychological medicine unit

The changing pattern of HIV infection in the UK includes an increase in the number of infections acquired as a result of heterosexual contact and Black African individuals represent a sizeable proportion of those affected. In most UK centres for the treatment of HIV infection, clinicians have limited experience in caring for Black African patients, and there is a dearth of information about the recognition and management of mental health problems in this patient group. In this investigation the proportion of Black African individuals looked after in a large centre for the care of HIV infection in London was compared with the proportion of such patients referred for specialist mental health help, the results revealing that Black Africans were almost three times less likely to be referred for specialist mental health care. A case control investigation of those referred to mental health services showed that Black Africans were more likely to be suffering from AIDS at the time of referral, be referred for assessment of possible organic brain disease, and more likely to be found to be suffering from major depression or organic brain disease. Reasons for the lesser likelihood of referral to the mental health service are considered, including the possible failure of staff to recognize psychological morbidity in Black Africans, or reluctance and fear on the part of patients to be referred to services that may be perceived as threatening.

The effect of hydroxyl radicals on the rheological performance of hylan and hyaluronan

Shear flow, dynamic oscillation and extensional viscosity measurements were used to compare the rheological performance of several hylan samples (M(v) 1.6, 3.2, 3.7, 4.7 and 5.6x10(6)) and hyaluronan (M(v) 1.4 and 1.8x10(6)) before and after hydroxyl radicals (*OH) induced degradation. It was found that the higher molecular weight cross-linked structure of hylan was more resistant to degradation than hyaluronan and that this superior stability was reflected in various rheological parameters. The *OH degradation of the initial hylan and hyaluronan samples produced a range of polysaccharides based on hylan and hyaluronan with molecular weight covering a range from 0.5-5.6x10(6). The rheological parameters associated with the polysaccharides could then also be studied. Zero shear values of the complex viscosity (eta*), dynamic viscosity (eta') and shear viscosity (eta) were calculated using the method of Morris(1) and shown to approach the same value at zero shear or frequency. An adaptation of the method of Gibbs et al. gave a 'master curve' for the storage and loss modulus of hyaluronan and hylan, which encompasses a 10-fold molecular weight and a 5-fold concentration variation. In all instances for hylan, the storage modulus predominates over the loss modulus, whereas for hyaluronan, the reverse is true, demonstrating the greater elasticity of hylan throughout the whole experimental range of molecular weights and concentrations.

The changing pattern of mental health problems in HIV infection: the view from London, UK

As we end the second decade with AIDS, profound changes in our understanding of its aetiology, mechanism of disease and its treatment have led to significant improvements in survival, disease progression and quality of life for those individuals with HIV infection who are fortunate enough to have access to health care and to treatments for the infection and its complications. Unsurprisingly, the psychological and social consequences of HIV have also seen important shifts, giving rise to new and unforeseen difficulties, as well as a greater sense of hope. Here, some of the changes seen among people with HIV infection being looked after in a Central London teaching hospital and referred to the mental health services are reviewed and discussed.