Building on Quicksand

Reliable systems have always been built out of unreliable components. Early on, the reliable components were small such as mirrored disks or ECC (Error Correcting Codes) in core memory. These systems were designed such that failures of these small components were transparent to the application. Later, the size of the unreliable components grew larger and semantic challenges crept into the application when failures occurred. As the granularity of the unreliable component grows, the latency to communicate with a backup becomes unpalatable. This leads to a more relaxed model for fault tolerance. The primary system will acknowledge the work request and its actions without waiting to ensure that the backup is notified of the work. This improves the responsiveness of the system. There are two implications of asynchronous state capture: 1) Everything promised by the primary is probabilistic. There is always a chance that an untimely failure shortly after the promise results in a backup proceeding without knowledge of the commitment. Hence, nothing is guaranteed! 2) Applications must ensure eventual consistency. Since work may be stuck in the primary after a failure and reappear later, the processing order for work cannot be guaranteed. Platform designers are struggling to make this easier for their applications. Emerging patterns of eventual consistency and probabilistic execution may soon yield a way for applications to express requirements for a "looser" form of consistency while providing availability in the face of ever larger failures. This paper recounts portions of the evolution of these trends, attempts to show the patterns that span these changes, and talks about future directions as we continue to "build on quicksand".Comment: CIDR 200

Student Health Services

This departmental history was written on the occasion of the UND Quasquicentennial in 2008.https://commons.und.edu/departmental-histories/1097/thumbnail.jp

Long-term impact of sewage sludge application on soil microbial biomass: An evaluation using meta-analysis

The Long-Term Sludge Experiments (LTSE) began in 1994 as part of continuing research into the effects of sludge-borne heavy metals on soil fertility. The long-term effects of Zn, Cu, and Cd on soil microbial biomass carbon (Cmic) were monitored for 8 years (1997-2005) in sludge amended soils at nine UK field sites. To assess the statutory limits set by the UK Sludge (Use in Agriculture) Regulations the experimental data has been reviewed using the statistical methods of meta-analysis. Previous LTSE studies have focused predominantly on statistical significance rather than effect size, whereas meta-analysis focuses on the magnitude and direction of an effect, i.e. the practical significance, rather than its statistical significance. The results presented here show that significant decreases in Cmic have occurred in soils where the total concentrations of Zn and Cu fall below the current UK statutory limits. For soils receiving sewage sludge predominantly contaminated with Zn, decreases of approximately 7–11% were observed at concentrations below the UK statutory limit. The effect of Zn appeared to increase over time, with increasingly greater decreases in Cmic observed over a period of 8 years. This may be due to an interactive effect between Zn and confounding Cu contamination which has augmented the bioavailability of these metals over time. Similar decreases (7–12%) in Cmic were observed in soils receiving sewage sludge predominantly contaminated with Cu; however, Cmic appeared to show of recovery after a period of 6 years. Application of sewage sludge predominantly contaminated with Cd appeared to have no effect on Cmic at concentrations below the current UK statutory limit

Referrals between Public Sector Health Institutions for Women with Obstetric High Risk, Complications, or Emergencies in India - A Systematic Review.

Emergency obstetric care (EmOC) within primary health care systems requires a linked referral system to be effective in reducing maternal death. This systematic review aimed to summarize evidence on the proportion of referrals between institutions during pregnancy and delivery, and the factors affecting referrals, in India. We searched 6 electronic databases, reviewed four regional databases and repositories, and relevant program reports from India published between 1994 and 2013. All types of study or reports (except editorials, comments and letters) which reported on institution-referrals (out-referral or in-referral) for obstetric care were included. Results were synthesized on the proportion and the reasons for referral, and factors affecting referrals. Of the 11,346 articles identified by the search, we included 232 articles in the full text review and extracted data from 16 studies that met our inclusion criteria Of the 16, one was RCT, seven intervention cohort (without controls), six cross-sectional, and three qualitative studies. Bias and quality of studies were reported. Between 25% and 52% of all pregnancies were referred from Sub-centres for antenatal high-risk, 14% to 36% from nurse run delivery or basic EmOC centres for complications or emergencies, and 2 to 7% were referred from doctor run basic EmOC centres for specialist care at comprehensive EmOC centres. Problems identified with referrals from peripheral health centres included low skills and confidence of staff, reluctance to induce labour, confusion over the clinical criteria for referral, non-uniform standards of care at referral institutions, a tendency to by-pass middle level institutions, a lack of referral communication and supervision, and poor compliance. The high proportion of referrals from peripheral health centers reflects the lack of appropriate clinical guidelines, processes, and skills for obstetric care and referral in India. This, combined with inadequate referral communication and low compliance, is likely to contribute to gaps and delays in the provision of emergency obstetric care

Transport of pregnant women and obstetric emergencies in India: an analysis of the '108' ambulance service system data.

BACKGROUND: The transport of pregnant women to an appropriate health facility plays a pivotal role in preventing maternal deaths. In India, state-run call-centre based ambulance systems ('108' and '102'), along with district-level Janani Express and local community-based innovations, provide transport services for pregnant women. We studied the role of '108' ambulance services in transporting pregnant women routinely and obstetric emergencies in India. METHODS: This study was an analysis of '108' ambulance call-centre data from six states for the year 2013-14. We estimated the number of expected pregnancies and obstetric complications for each state and calculated the proportions of these transported using '108'. The characteristics of the pregnant women transported, their obstetric complications, and the distance and travel-time for journeys made, are described for each state. RESULTS: The estimated proportion of pregnant women transported by '108' ambulance services ranged from 9.0 % in Chhattisgarh to 20.5 % in Himachal Pradesh. The '108' service transported an estimated 12.7 % of obstetric emergencies in Himachal Pradesh, 7.2 % in Gujarat and less than 3.5 % in other states. Women who used the service were more likely to be from rural backgrounds and from lower socio-economic strata of the population. Across states, the ambulance journeys traversed less than 10-11 km to reach 50 % of obstetric emergencies and less than 10-21 km to reach hospitals from the pick-up site. The overall time from the call to reaching the hospital was less than 2 h for 89 % to 98 % of obstetric emergencies in 5 states, although this percentage was 61 % in Himachal Pradesh. Inter-facility transfers ranged between 2.4 % -11.3 % of all '108' transports. CONCLUSION: A small proportion of pregnant women and obstetric emergencies made use of '108' services. Community-based studies are required to study knowledge and preferences, and to assess the potential for increasing or rationalising the use of '108' services

What do Indian children drink when they do not receive water?:statistical analysis of water and alternative beverage consumption from the 2005-2006 Indian National Family Health Survey

BACKGROUND: Over 1.2 billion people lack access to clean water. However, little is known about what children drink when there is no clean water. We investigated the prevalence of receiving no water and what Indian children drink instead. METHODS: We analysed children's beverage consumption using representative data from India's National Family and Health Survey (NFHS-3, 2005-2006). Consumption was based on mothers' reports (n = 22,668) for children aged 6-59 months (n = 30,656). RESULTS: About 10 % of Indian children had no water in the last 24 h, corresponding to 12,700,000 children nationally, (95 % CI: 12,260,000 to 13,200,000). Among children who received no water, 23 % received breast or fresh milk and 24 % consumed formula, "other liquid", juice, or two or more beverages. Children over 2 were more likely to consume non-milk beverages, including tea, coffee, and juice than those under 2 years. Those in the lowest two wealth quintiles were 16 % less likely to have received water (OR = 0.84; 95 % CI: 0.74 to 0.96). Compared to those living in households with bottled, piped, or tanker water, children were significantly less likely to receive water in households using well water (OR = 0.75; 95 % CI: 0.64 to 0.89) or river, spring, or rain water (OR =0.70; 95 % CI: 0.53 to 0.92) in the last 24 h. CONCLUSIONS: About 13 million Indian children aged 6-59 months received no water in the last 24 h. Further research is needed to assess the risks potentially arising from insufficient water, caffeinated beverages, and high sugar drinks at early stages of life