Hypothesis testing in hedonic price estimation – On the selection of independent variables

Various approaches to hypothesis testing have been used in the past for the purpose of estimating hedonic price equations. The criteria for testing and rejecting explanatory variables have however rarely been made explicit. This paper argues that the results of earlier studies should be used according to structured and not overly arbitrary criteria for selecting which variables to test as well as for their subsequent acceptance or rejection. An explanatory analysis of Singapore's condominium market is used as an empirical illustration of the decision rule for variable selection proposed in the methodological part of the paper. Received: March 1998/Accepted: May 1999     

Nasal histamine reactivity among adolescents in a remediated moisture-damaged school--a longitudinal study

In a previous study, in the spring of 1995, we found that teachers, who had been working for several years in a moister-damaged school, 1 year after the renovation still reported a higher frequency of complaints and symptoms and showed significantly higher mucosal histamine reactivity compared with teachers in a control school, although the school seemed to be properly renovated. A longitudinal study of 90 randomly selected senior high school students entering the two schools was initiated to exclude or verify if the indoor air still exerted an irritant effect on the upper airways of an earlier unexposed group. The students went through a nasal histamine provocation test and answered a questionnaire on three occasions, in 1995, 1996 and 1997. No significant differences in the nasal histamine provocation curves for the students at the target school and those at the control school could be shown from start to endpoint of the study period. Neither was there any differences concerning perceived indoor air or mucosal symptoms between the target and the control group and technical measurements showed no noteworthy differences between the two schools. In conclusion, this study indicates that based on both technical and objective medical measures, the current indoor air in the remediated moisture-damaged school does not exert an irritant effect on the upper airway mucosa of the students. A 2-year follow-up of the teachers showed a decreased reactivity to histamine, giving further support to this statement. The increased mucosal reactivity observed among the teachers is probably a result of the previous long-term exposure to building dampness. No differences were seen between atopic and non-atopic students. PRACTICAL IMPLICATIONS: Persistent symptoms and increased nasal mucosal reactivity among personnel in a remediated damp building does not necessary imply an inadequate renovation. A longitudinal study with registration of subjective (questionnaires) and objective (nasal histamine reactivity) data of an earlier unexposed group residing in the same building further contributes to the evaluation whether the renovation was successful or not.     

Vauxhall’s post-industrial pleasure gardens: "death wish" and hedonism in 21st-century London

In recent years Vauxhall in south London has been transformed and rebranded as an urban leisure zone for gay men. Disused railway arches and warehouses have been converted into nightclubs and a significant night-time economy has developed rivalling Soho's existing gay village. However, with its commodified forms of public sex and high levels of recreational drug use, Vauxhall's club scene looks rather different from the British gay villages of the 1990s. This article examines how the area's nightlife entrepreneurs have capitalised on the recent liberalisation of licensing laws while drawing on the historical associations with the Vauxhall Pleasure Gardens (1660-1859) in attempts to market the area as a site of embedded hedonism. Overall, the aesthetic and cultural themes of Vauxhall's club scene seem to contradict earlier assumptions about the desexualisation and sanitisation of contemporary gay culture.     

Application of two-level factorial design to sensitivity analysis of keyblock statistics from fracture geometry

A stochastically modeled fracture network offers potential for more realistic assessment of stability status in underground excavations than predictions based entirely on deterministic features. The reliability of probabilistic models, however, depends strongly on an accurate estimation of the model's variables, i.e., the fracture network properties from the field and laboratory observations.In this study, predictions of keyblocks by implementing stochastically generated fractures in the Central Storage Facility for Spent Nuclear Fuel (CLAB 2 Centralt Lager Använt Bränsle) located in southeast Sweden are presented. The fracture network model is built by using fracture mapping in the floor of the facility and incorporates fracture size, shape, orientations, termination mode, spatial arrangement and fracture mechanical properties. The predicted volume of individual keyblocks is best-fitted with the Pareto probability distribution function. Subsequently, a statistical two-level factorial analysis is performed to examine the impact of both single fracture properties and their interactions on the predictions made. In the factorial experiments, the block predictions are made for eight different fracture models where three factors: fracture radii, orientation and termination are each assigned two levels intentionally departing from the best estimates found for the CLAB 2 site. This allows us to express the experiment results as the degree to which each of the eight computed block statistics deviated from the most likely prediction. It is found that fracture orientation is the only statistically significant factor influencing the keyblock statistics while the input from other variables/fracture properties and their interactions is less significant.The results of our study yield a prospective approach for improving the effectiveness of the stochastic model variable estimation and for more optimal field mapping strategies.     

Dyspepsia in general practice: history and symptoms in relation to Helicobacter pylori serum antibodies

The stereoselectivity of Baker's yeast reduction of prochiral alpha-oxygenated 2-propanones has been studied by varying the substrate structure. The 1-hydroxy-3-methoxy-3-propanone 1a was reduced to the corresponding alcohol (R)-2a with 88% enantiomeric excess. Replacing the hydroxy group in 1a with phenoxy or benzyloxy (1b and 1c) gave the alcohols (S)-2b and (S)-2c with 53 and 32% ee, respectively. Reduction of the methyl ketone 1d gave the alcohol (S)-2d with 91% ee. Attempts to improve the enantioselectivity of the reduction of 1c by lowering the substrate concentration or addition of selective reductase inhibitors had only small effect on the enantioselectivity.     

Recovery from left ventricular asynergy in ischemic cardiomyopathy following long-term beta blockade treatment

Many environmental pollutants interact with solar near-ultraviolet (nuv) light in a manner which greatly increases their toxic effects. The phenomenon of light-mediated toxicity (phototoxicity) is only now becoming generally recognized to any significant degree. Manufacture of, and loading munitions with, the explosive 2,4,6-trinitrotoluene (TNT) in past decades caused contamination of soils and sediments at levels exceeding 1000 ppm and of waters at levels near saturation (100 ppm). Manufacture of TNT produces numerous nitrated by-products, and most of these compounds, including TNT, can be metabolized by many species, including bacteria, fungi, plants, and mammals. This study investigated the phototoxicity of TNT, and 2,3-, 2,4-, 2,6-, and 3,4-dinitrotoluene (DNT) and -diaminotoluene (DAT), and the major metabolites 2-amino-4,6-dinitrotoluene (2A) and 4-amino-2,6-dinitrotoluene (4A), to Daphnia magna (acute toxicity) and Lytechinus variagatus (sea urchin) embryos (subacute, developmental toxicity). Most of the compounds were weakly toxic or nontoxic in the dark. All were phototoxic to sea urchins. In D. magna, 2,3- and 3,4-DNT/DAT and 4A were not toxic but were phototoxic, and 2A was toxic and phototoxic; the other isomers were not toxic or phototoxic to this species.     

First use of an untethered, vented electric left ventricular assist device for long-term support

This report describes the first long-term (505-day) application of the vented electric (VE) HeartMate left ventricular assist device (LVAD) (Thermo Cardiosystems, Inc). The device consists of an abdominally placed, battery-powered titanium blood pump that, in contrast to earlier pneumatically powered systems, allows patients untethered freedom of movement. The batteries last 5 to 8 hours and can be changed on a rotating basis indefinitely. The patient, a 33-year-old man (90 kg, blood type O) with idiopathic cardiomyopathy, experienced end-organ heart failure (New York Heart Association [NYHA] class IV) while he was awaiting heart transplantation. When his hemodynamic criteria met those outlined in the protocol, we implanted the VE-LVAD as a bridge to transplantation. The patient was supported by the device for more than 16 months. His cardiac status returned to NYHA class I, and he was eventually allowed to take day trips outside the hospital as he awaited transplantation. The VE-LVAD enabled the patient to participate in activities such as eating in restaurants, going to movies, and practicing basketball shots. Unfortunately, the patient died suddenly due to a neurological thromboembolic event that occurred on day 503 of VE-LVAD support. The VE-LVAD improved native left ventricular function by chronic unloading, and ventricular remodeling resulted in a more normal configuration anatomically, physiologically, and ultimately, histologically and pathologically.     

Influence of anti-inflammatory and antioxidant agents on endothelial permeability alterations induced by bradykinin

Increased vascular permeability to plasma proteins and altered hemodynamics at the site of inflammation are characteristics of inflammation. In the present study, alterations in endothelial barrier permeability were evaluated in different organs/tissues 6 h after a systemic inflammatory response induced by intravenous injection of bradykinin (BK; 1.7 mg/kg). The effect of intravenous pretreatment with indomethacin or ibuprofen (cyclooxygenase inhibitors), N-acetyl-L-cysteine (NAC, an oxygen free radical scavenger), and allopurinol (a xanthine oxidase inhibitor) was determined. Endothelial permeability was evaluated by determining tissue water content (TWC), 125I-labeled human serum albumin (HSA) flux, and albumin leakage index (ALI) in various organs/tissues. The vasodilation in the local tissues was reflected by tissue blood content (TBC), measured by 51Cr-labeled red blood cells. The results indicate that albumin flux significantly increased in the peritoneum, pancreas, stomach, PSI, DSI, colon, kidneys, liver, lungs, and brain, TBC significantly increased in the kidneys, liver, lungs, and heart, as well as in the intestine, and an increased ALI, assaying endothelial permeability considering local hemodynamic alterations was noted in the pancreas, kidneys, liver, lungs, PSI, and DSI in the group with BK alone. These changes were to varying degrees reversed by pretreatment with indomethacin, ibuprofen, N-acetyl-L-cysteine, or allopurinol, where the protective effect tended to be organ-dependent.