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PubMed1970

The effect of high vacuum on oxidative reactions in bacteria and the activity of certain enzymes.

Among the physical factors which might influence micro-organisms one of the most potentially interesting is high vacuum. The effect of high vacuum is less studied as compared with other physical factors. It is impossible to achieve, under laboratory conditions, a vacuum of the order 10(-16) mm Hg which is probably characteristic of space. Earlier, the effect of high vacuum was studied on different bacteria, yeasts, molds and algae. It appeared that spores and fungal conidia were not killed by high vacuum. Later, the effect of high vacuum on physiological processes in micro-organisms was studied. The ability to oxidize glucose or ethanol was studied with Sarcina flava and Bacillus simplex cells after they were subjected for 72 hr to vacuum (10(-8) to 10(-9) mm Hg). The oxidation rate was followed polarographically. The oxidative ability of S. flava cells diminished [correction of dimished] after their subjection to vacuum, while B. simplex spores were unchanged in that respect. The following crystalline enzymes were subjected for 72 hr to the same vacuum: alpha-amylase, catalase, ribonuclease, trypsine and urease. Then the activity of the above enzymes was tested on corresponding substrates. Not a single enzyme was totally inactivated. About 50% of activity was lost with alpha-amylase; 25--35% of activity with catalase, ribonuclease and urease. Trypsine retained its total activity. Thus, high vacuum cannot be listed among factors rapidly inactivating enzymes of micro-organisms.

Bacillus↗
PubMed2003

Randomised clinical trial to assess anal sphincter function following forceps or vacuum assisted vaginal delivery.

OBJECTIVE: To compare, in a prospective, randomised controlled trial, differences in anal sphincter function following forceps or vacuum assisted vaginal delivery in an institution practising standardised management of labour. DESIGN: Prospective, randomised controlled trial. SETTING: Tertiary-referral maternity teaching hospital. POPULATION: One hundred and thirty women. METHODS: Primiparous women were recruited antenatally and if an instrumental delivery was indicated, were randomised to either a vacuum or low-cavity, non-rotational forceps assisted delivery. Follow up consisted of a symptom questionnaire, anal manometry and endoanal ultrasound at three months postpartum. MAIN OUTCOME MEASURES: Faecal continence scores, anal manometry, endoanal ultrasound. RESULTS: Sixty-one women delivered with forceps assistance (40 for failure to progress in the second stage) and 69 with vacuum assistance (33 for failure to progress); 16/69 vacuum deliveries proceeded to a forceps assisted delivery (23%). There were no statistical differences in the antecedent antenatal factors between the two groups. A third degree perineal tear followed 10 (16%) forceps and 5 (7%) vacuum deliveries. Based on intention-to-treat analysis, 36 (59%) women complained of altered faecal continence after forceps delivery compared with 23 (33%) following vacuum delivery three months postpartum (RR 2.88, 95% CI 1.41-5.88). Endoanal ultrasound was reported as abnormal following 34 (56%) forceps deliveries and 34 (49%) vacuum deliveries (RR 1.3, 95% CI 0.65-258). After exclusion of 'failed vacuum', median anal canal resting pressure was significantly lower following forceps delivery compared with vacuum delivery alone (P = 0.004). There were no significant differences in degree of ultrasound abnormality between the two groups. CONCLUSIONS: Symptoms of altered faecal continence are significantly more common following forceps assisted vaginal delivery. Based on continence outcome, when circumstances allow, vacuum should be the instrument of first choice in assisted delivery.

Adult↗
PubMed1987

Vacuum extraction versus forceps delivery: indications and complications, 1979 to 1984.

Two hundred fifty-six vacuum extractions and 300 randomly chosen forceps deliveries were analyzed retrospectively. Vacuum extraction use increased from 0.3 to 3.1%, while forceps use declined from 10.1 to 4.9% over a five-year period. No differences were found in indications for vacuum extraction and forceps, but the preapplication position differed (occiput posterior or transverse in 81.2% in the vacuum group and 27% in forceps patients). Preapplication station also differed, with 59.8% of vacuum extraction at +1 or higher stations, compared with 9% of forceps. Under these conditions we found less maternal trauma, similar failure rates (3.9 versus 2%), and no difference in maternal morbidity. There was a higher incidence of shoulder dystocia and neonatal jaundice in the vacuum group, but cephalohematoma frequency did not differ significantly (3.9% vacuum extraction, 4.3% forceps). Cosmetic injuries (ecchymoses, abrasions) were more likely with vacuum extraction than with forceps (44.1 versus 29.5%). One death occurred in each group. Vacuum extraction replaced midforceps in our institution in the study period. We consider vacuum extraction a useful technique to teach house staff in view of today's decreasing instrumental delivery rate.

Birth Injuries↗
PubMed2003

Vacuum-assisted closure as a treatment modality for infections after cardiac surgery.

OBJECTIVE: Wound infections after cardiac surgery carry high morbidity and mortality. A plethora of management strategies have been used to treat such infections. We assessed the impact of vacuum-assisted closure on the management of sternal wound infections in terms of wound healing, duration of vacuum-assisted closure, and cost of treatment. METHODS: Between November 1998 and June 2001, a total of 27 mediastinal infections were managed with vacuum-assisted closure. Group A (n = 14) had vacuum-assisted closure as the final treatment modality, whereas in group B (n = 13) vacuum-assisted closure was followed by either a myocutaneous flap (n = 8) or primary (n = 5) wound closure. The choice of additional treatment modality was based on wound size. RESULTS: In group A, 4 patients died and a satisfactorily healed scar was achieved in 64% of cases. Median durations of vacuum-assisted closure and hospital stay in group A were 13.5 days (interquartile range 8.8-32.2 days) and 20 days (interquartile range 16.7-25.2 days), respectively. Mortality was 7.7% in group B, with a treatment failure rate of 15%. Median duration of vacuum-assisted closure in group B was 8 days (interquartile range 5.5-18 days), and median hospital stay was 29 days (interquartile range 25.8-38.2 days). During the year before institution of vacuum-assisted closure, poststernotomy infection (n = 13) was managed with rewiring and closed irrigation system. Treatment during this year failed in 30.7% of cases (n = 4/13), and mortality was also 30.7%. The total cost (hospitalization and treatment) per patient for vacuum-assisted closure was 16,400 dollars, compared with 20,000 dollars for the closed irrigation system treatment. CONCLUSION: Vacuum-assisted closure, used alone or before other surgical treatment strategies, is an acceptable treatment modality for infections in cardiac surgery with reasonable morbidity, mortality, and cost.

Adult↗
PubMed1995

Effects of vacuum UV and UVC radiation on dry Escherichia coli plasmid pUC19. II. Mutational specificity at the lacZ gene.

The mutational spectra at the lacZ gene, induced either by vacuum UV at 160 nm or UVC at 254 nm in vacuum-dried preparations of Escherichia coli plasmid pUC19 DNA, have been characterized from 72 E. coli-propagated mutants by DNA sequencing. In plasmids irradiated in vacuum, vacuum UV is five times more mutagenic than UVC. In the UV-induced mutants, base substitutions largely predominate, with GC-->AT (G, guanine; C, cytosine; A, adenine; T, thymine) transitions being the most abundant type of base change for vacuum UV (61%) and UVC (47%). Most of the GC-->AT transitions appear to occur at dipyrimidine sites, which are located at the non-transcribed DNA strand. Some, but not all, hot spots for GC-->AT transitions are identical for vacuum UV and UVC. Frameshifts, resulting from a loss of the thymine residue, are specific for UVC (22%), and were not detected after treatment with vacuum UV. They occur predominantly at thymine runs of the transcribed DNA strand. Only a few deletions were detected following irradiation with vacuum UV (7.5%) and UVC (2%); however, their frequency is not enhanced compared with the spontaneous mutation spectrum. The data confirm the important role of base substitution mutations in UV-induced mutagenesis, which is not only valid for the UVC range, but extends towards the vacuum UV range.

Base Sequence↗
PubMed2004

Survival of mammalian cells under high vacuum condition for ion bombardment.

An ion beam has been used to irradiate various organisms and its effects have been studied. Because of the poor tolerance that mammalian cells have for vacuum, such studies have not been carried out on living mammalian cells until now. However, this work is important both for elucidating the mechanism of mutation in response to low-energy ions and in exploring possible new applications of ion beam technology. The current paper describes an investigation of the survival of mammalian cells (the A(L) cell line) in a high-vacuum chamber in preparation for ion bombardment studies. The ion beam facility is described and the actual vacuum profile that the cells endured in the target chamber is reported. Cells were damaged immediately following vacuum exposure; the injury was characterized by alteration of the membrane permeability, loss of firm adhesion to the dish, and increased fragility. Three cryoprotective agents were tested (glycerol, propylene glycol, and trehalose) and of these, glycerol showed the highest potency for protecting cells against vacuum stress. This was revealed by an increase in the cell survival level from <1 to >10% with a glycerol concentration of 15 and 20%. Two glycerol-based protocols were investigated (freezing-vacuum vs. non-freezing-vacuum), but there was no significant difference (P > 0.1) in their ability to improve cell survival, the values being 10.31 +/- 4.5 and 12.7 +/- 3.37%, respectively with 20% glycerol concentration. These cells had a normal growth capability, and also retained integrity of the cell surface antigen CD59. These initial experiments indicate that mammalian cells can withstand vacuum to the degree that is needed to study the effect of the ion beam. In addition to the improvements made in this study, other factors are discussed that may increase the survival of mammalian cells exposed to a vacuum in future studies.

Animals↗
PubMed2006

Development of a vacuum filtration system for the conventional microplate washer.

INTRODUCTION: Filter plates are available from many vendors reflecting the growth of their scientific applications in various fields, however, the heterogeneous nature of those applications are the major factor to block the expansion of various filter plate options in a research scale operation. The development of an automatic vacuum filtration system for a conventional plate washer was presented as a possible solution for the filtration process in filter plate applications, especially in the melanin concentrating hormone receptor subtype 1 (MCH1) receptor binding assay with the time resolved fluorescence technology. METHODS: The pilot modification was done in the Embla 96/384 well washer by replacing the original plate carriage with a new carriage mimicking the conventional vacuum manifold to add the function of flow-through vacuum filtration for filter plates. The performance of new vacuum filtration system was evaluated with MCH1 receptor binding assay and ligand washout experiments. RESULTS: The mean background values from ligand washout experiments in AcroWell filter plates were 6406+/-502.9 with a manual vacuum manifold and 5563+/-585.8 with the vacuum filtration system. Z' factors were calculated as 0.6101+/-0.095 for the MCH1 receptor binding assay with the vacuum filtration system. DISCUSSION: The new plate carriage for a conventional plate washer was developed for filter plate applications to enable its use in a flow-through vacuum filtration application in addition to the conventional plate washing by an aspiration. The results from ligand washout and receptor binding assay suggest that the vacuum filtration system can provide a cost-effective solution for filter plate applications and may alleviate the most common problems of those heterogeneous assays to develop as high throughput operations without major investments for the professional workstations.

Animals↗
PubMed2003

Vacuum-assisted venous return reduces blood usage.

OBJECTIVE: To determine whether vacuum-assisted venous return has clinical advantages over conventional gravity drainage apart from allowing the use of smaller cannulas and shorter tubing. METHODS: A total of 150 valve operations were performed at our institution between February and July 1999 using vacuum-assisted venous return with small venous cannulas connected to short tubing. These were compared with (1) 83 valve operations performed between April 1997 and January 1998 using the initial version of vacuum-assisted venous return, and (2) 124 valve operations performed between January and April of 1997 using conventional gravity drainage. Priming volume, hematocrit value, red blood cell usage, and total blood product usage were compared multivariably. These comparisons were covariate and propensity adjusted for dissimilarities between the groups and confirmed by propensity-matched pairs analysis. RESULTS: Priming volume was 1.4 +/- 0.4 L for small-cannula vacuum-assisted venous return, 1.7 +/- 0.4 L for initial vacuum-assisted venous return, and 2.0 +/- 0.4 L for gravity drainage (P <.0001). Smaller priming resulted in higher hematocrit values both at the beginning of cardiopulmonary bypass (27% +/- 5% compared with 26% +/- 4% and 25% +/- 4%, respectively, P <.0001) and at the end (30% +/- 4% compared with 28% +/- 4% and 27% +/- 4%, respectively, P <.0001). Red cell transfusions were used in 17% of the patients having small-cannula vacuum-assisted venous return, 27% of the initial patients having vacuum-assisted venous return, and 37% of the patients having gravity drainage (P =.001); total blood product usage was 19%, 27%, and 39%, respectively (P =.002). Although ministernotomy also was associated with reduced blood product usage (P <.004), propensity matching on type of sternotomy confirmed the association of vacuum-assisted venous return with lowered blood product usage. CONCLUSIONS: Vacuum-assisted venous return results in (1) higher hematocrit values during cardiopulmonary bypass and (2) decreased red cell and total blood product usage.

Blood Circulation↗
PubMed1997

A randomized trial of two vacuum extraction techniques.

OBJECTIVE: To determine whether two techniques of vacuum extraction delivery-continuous vacuum and intermittent vacuum-have different effects on maternal-fetal outcomes. METHODS: Patients to be delivered by vacuum extraction were randomized to receive continuous or intermittent vacuum. All deliveries were performed using the M-cup. In the continuous group, the level of vacuum was brought to 600 mmHg between contractions and was maintained at that level until delivery of the infant. Active efforts were made to prevent fetal loss-of-station between contractions by maintaining traction. In the intermittent group, the level of vacuum was decreased to 100 mmHg between contractions and no effort was made to prevent fetal loss-of-station. RESULTS: A total of 322 patients were randomized: 164 in the continuous arm and 158 in the intermittent group. The continuous method did not effect delivery faster (continuous 167 +/- 175 seconds versus intermittent 167 +/- 150 seconds; P = .97), nor did it lead to a reduction in method failures (continuous 12, intermittent nine; P = .72). The intermittent method did not appear to offer any benefit to the neonate regarding cephalhematoma formation (continuous 20, intermittent 17; P = .686) or any other measure of neonatal outcome. Maternal lacerations and episiotomy extensions were evenly distributed between the groups. Overall, the efficacy rate of the vacuum cup was 93.5% and the cephalhematoma rate was 11.5%. CONCLUSION: No differences in maternal or fetal outcome could be demonstrated if the level of vacuum was decreased between contractions or if an effort was made to prevent fetal loss-of-station. The clinical results obtained in this trial using the M-cup are similar to the published results with the stainless-steel Malmstrom cup.

Adult↗
PubMed1995

Effects of vacuuming on dye penetration patterns in root canals and glass tubes.

This study compared the dye leakage pattern of prepared root canals with that of glass tubes, with and without vacuuming. The apical 12 mm of 40 calcified root canals were prepared to tubes with a diameter of 0.5 mm. The coronal end of these canals and 40 glass tubes with similar diameters (12 mm x 0.5 mm) were closed with 2 mm of Cavit. Twenty samples from each group were left empty, and the rest (20) were filled with gutta-percha without sealer. Half of the samples of filled (10) and unfilled (10) specimens were then placed horizontally in 2% methylene blue dye. The other half (10) of the samples from each group were placed in a vacuum (25 mm Hg) and submerged in the dye. Leakage was then measured in millimeters and statistically analyzed using analysis of variance. The 20 empty glass tubes with or without vacuum leaked 17% or less of their lengths. The 20 glass tubes filled with gutta-percha averaged 70.5% leakage. Of those, the 10 glass tubes that were vacuumed had 100% leakage. Empty root canals exhibited mean leakage of 74% without vacuum and 91% of their length with vacuum. Canals filled with gutta-percha leaked a mean of 95.5% of their entire lengths without vacuum and 100% with vacuum (no significant difference). The results showed that filled and unfilled, prepared root canals leaked significantly more than their glass tube counterparts (p < 0.001), and vacuuming may not be necessary for dye leakage studies in filled root canals.

Air↗
PubMed2005

Risk factors for obstetric brachial plexus palsy among neonates delivered by vacuum extraction.

OBJECTIVE: The risk of obstetric brachial plexus palsy (OBPP) is increased in infants delivered instrumentally. The aim of this study was to identify risk factors for OBPP and to evaluate the association between possible risk factors linked to the duration of the vacuum extraction procedure and the subsequent risk. METHODS: A population-based retrospective design was adopted. Using a national registry of operative vaginal deliveries linked to the Medical Birth Registry in Sweden, we evaluated by univariate and multiple logistic regression analyses the risk factors for OBPP in 13,716 women delivered by vacuum extraction. The variables assessed in the multiple logistic regression analysis were shoulder dystocia, fetal birth weight of 3,999 g or greater, fundal pressure, number of tractions, vacuum application time, parity, vacuum silicone cup, epidural anesthesia, and fetal head at the level of the ischial spines at vacuum application time. RESULTS: Obstetric brachial plexus palsy was recorded in 153 (1.1%) infants. The following variables increased significantly the risk of OBPP in the newborn: shoulder dystocia (odds ratio 16.0; 95% confidence interval 8.9-28.7), fetal birth weight of 3,999 g or greater (7.1; 4.8-10.5), and administration of fundal pressure (1.6; 1.1-2.3). The probability of the risk of OBPP in vacuum-assisted deliveries increased in relation to vacuum extraction time (minutes). CONCLUSION: Shoulder dystocia in the setting of vacuum extraction is a prominent risk factor for OBPP in the newborn. The risk of OBPP increases with the time required for vacuum extraction. LEVEL OF EVIDENCE: II-3.

Adult↗
PubMed2004

[Standard versus "hand-pump" vacuum extraction device].

OBJECTIVE: Clinical evaluation of a standard vacuum delivery device and "hand-pump" vacuum delivery device. DESIGN: Retrospective clinical study. SETTING: Department of Obstetrics and Gynecology, City Hospital, Litomĕrice. METHODS: In the period between January 1993 and the end of December 2003 there were 81 deliveries by vacuum at our department, 55 of which (67.90%) were with standard vacuum delivery device and 26 (32.10%) with "hand-pump" vacuum delivery device. We evaluated the differences in the following parameters: 1. basic characteristics--maternal age, parity, gestational age, birth weight and type of labor, 2. early maternal morbidity--the presence of episiotomy, perineal and vaginal tears, blood loss, the need of blood transfusion, duration of hospitalization and postpartum incontinentia urinae and alvi, 3. early neonatal morbidity--pH a. umbilicalis, Apgar score and the presence of newborn's trauma. The differences found in individual groups were then used for statistics and evaluated. RESULTS: In comparison with standard vacuum delivery device the usage of "hand-pump" vacuum delivery device appears to be more convenient for its significantly higher reliability, especially due to construction and also for its favourable features at early neonatal morbidity. CONCLUSION: We have proved that the "hand-pump" vacuum delivery device is in comparison with standard vacuum delivery device more favourable with newborns and more convenient to use for its high reliability.

Female↗
PubMed1991

A randomized comparison of assisted vaginal delivery by obstetric forceps and polyethylene vacuum cup.

The assisted vaginal delivery methods of rigid obstetric forceps and polyethylene vacuum cup extraction were compared in a prospective, randomized study. The 99 women studied had all completed 35 full weeks' gestation, required attempted assisted vaginal delivery, and were randomly assigned to either attempted forceps or vacuum-assisted delivery. All presentations were cephalic, with stations ranging from +1 to +4. Neonates were evaluated at 24 hours by neonatal staff. The infants underwent intracranial ultrasound screening during the first 24 hours of life and ophthalmologic examination within 48 hours. Vaginal delivery was successful with the intended method in 83% of vacuum-assisted deliveries and in 78% of forceps deliveries (not statistically significant). Neonatal retinal hemorrhage was found in 17 and 38% (P less than .043) of the randomized forceps and vacuum deliveries, respectively. No intraventricular hemorrhage was found. Apart from associations between vacuum-assisted delivery and mild hyperbilirubinemia and neonatal retinal hemorrhage (of uncertain clinical significance), and between assisted forceps delivery and an increased potential for facial injury, neonatal outcomes did not differ significantly. Maternal outcomes also did not differ significantly. No significant differences in safety or efficacy were found between polyethylene cup vacuum extraction and rigid obstetric forceps-assisted vaginal delivery in this population of predominantly low-pelvic assisted deliveries. Patients delivered by sequential use of forceps after vacuum or by vacuum after failed forceps application did not suffer significantly increased morbidity relative to those delivered by forceps or vacuum alone. Use of alternate or sequential methods allowed an overall cesarean rate of 3% in this population.

Acid-Base Equilibrium↗
PubMed1996

Vacuum delivery at The Maternity Hospital Kuala Lumpur: a comparison of metal and silicone cups.

OBJECTIVE: To compare the advantages and disadvantages of the New Bird metal cups and silicone cups in terms of maternal and foetal outcome. To study the adverse effects and factors associated with failed vacuum deliveries. DESIGN: A prospective randomised study of all vacuum deliveries from 1 December 1991 to 31 April 1992. The Hanshin electrical vacuum pump was used. SETTING: A large obstetric unit-The Maternity Hospital Kuala Lumpur (MHKL). SUBJECTS: Seventy-two consecutive patients where vacuum deliveries were indicated. Forty had metal and 32 had silicone cups. Another 7 vacuum deliveries using the manual vacuum pump were excluded. MAIN OUTCOME MEASURES: Success rate of vaginal delivery, birth canal injuries, post-partum haemorrhage, duration of hospital stay, Apgar score, foetal injuries (scalp-ecchymosis, haematomas) neonatal jaundice, the rate of special care nursery (SCN) admission and neonatal mortality rate. RESULTS: Failure to deliver with silicone cups alone was 21.9% compared to 10% for metal cups alone. Material morbidities and serious foetal scalp injuries were almost the same in both cups. However, minor foetal scalp injuries were significantly lower with silicone cups. Maternal height and baby's weight had no independent predictive values for successful vacuum delivery. When the foetal head was palpable per abdomen, the failure rate was 54.5% compared to 8.2% when it was not. Failed vacuum deliveries were associated with increased maternal and foetal morbidities. CONCLUSION: Silicone cups and metal cups can be equally dangerous to the baby. Although our sample size was small, we recommend that vacuum delivery be avoided if the foetal head is palpable per abdomen.

Contraindications↗
PubMed1996

Effects of aspiration vacuum and needle diameter on cumulus oocyte complex morphology and developmental capacity of bovine oocytes.

The effects of aspiration vacuum and needle diameter on the morphology of the cumulusoocyte-complex (COC) and developmental capacity of the oocyte after IVF was studied in 2 experiments using a disposable ovum pick-up needle guidance system whose construction permits its use in vitro. In Experiment 1, the relationship was determined between the aspiration vacuum, expressed in millimetre of mercury, and the actual amount of water aspirated by the system, expressed in millilitre per minute. In Experiment 2, five different levels of aspiration vacuum for 3 different needle diameters (18g, 19g and 21g) were tested in slaughterhouse ovaries. The cumulus-oocyte complexes (COCs) were divided into 3 categories: 1) oocytes with a compact cumulus, 2) oocytes with an expanded cumulus and 3) naked oocytes. The results show that a change of needle diameter can triple the amount of fluid actually aspirated. The highest oocyte recovery rates are obtained when using the thickest needle (18-g), regardless of the aspiration vacuum. On the average, for all needle types, more oocytes are recovered at the highest aspiration vacuum. For all needle diameters, the proportion of oocytes surrounded by a compact cumulus decreases progressively as the vacuum increases. Regardless of the vacuum applied, thinner needles result in a higher proportion of recovered COCs with a compact cumulus. At a high aspiration vacuum, naked oocytes become predominant regardless of the needle diameter. The prevalence of blastocysts, expressed in proportion to the recovered COCs, decreases as the aspiration vacuum increases, being especially noticeable between 70 and 130 mm Hg.

Journal Article↗
PubMed1995

A comparison of the effect of conventional and filter vacuum cleaners on airborne house dust mite allergen.

The efficiency (dust collection and recirculation) of a conventional upright vacuum cleaner with a prototype vacuum bag (I) with pore size of 0.1 micron was compared with a standard vacuum cleaner bag (II), in the homes of 11 atopic asthmatic subjects with a known allergy to house dust mite. Four filter vacuum cleaners were assessed in pairs-the Vax 2000 with the Vorwerk VK121 ET340 (in 10 homes), and the Nilfisk GS90 'Allergy Vac' with the Bosch maxima 43 (in nine homes). All of the selected homes were vacuumed throughout (carpets and soft furnishings) for a 15 min period with each of the cleaners, and air was sampled simultaneously at 21 min-1 (Casella personal sampler). The weight of dust retrieved was recorded, and a sample of sieved dust (2 g) and the air filters were extracted to determine the concentrations of the major allergen, Der pI, by ELISA (ALK). No significant difference was observed in either total weight of dust, or airborne and dust concentrations of Der pI between using the conventional cleaner with vacuum bags I, or vacuum bags II. The Vax and the Vorwerk filter vacuum cleaners produced no measurable airborne Der pI concentrations during use in any of the 10 homes tested, whilst the Nilfisk produced airborne Der pI in two, and the Bosch in one of the nine homes tested. The Vorwerk retrieved significantly more dust from the floors than the Vax (P < 0.002). There was no significant difference in dust retrieval between the Nilfisk and the Bosch. All of the filter vacuum cleaners investigated produced lower concentrations of airborne Der pI, compared to the conventional cleaner with or without a special dust bag. However, the amount of dust and concentration/amount of Der pI that these cleaners actually retrieved, varied and the Vorwerk appeared most effective overall.

Air Pollution, Indoor↗
PubMed2006

The vertical distribution of house dust mite allergen in carpet and the effect of dry vacuum cleaning.

BACKGROUND: Carpets are large reservoirs of the dust mite allergen Der p 1. The effect of vacuum cleaning on the distribution of Der p 1 in carpets is poorly understood. METHODS: Samples were cut from 7 used household carpets, all over 5 years of age. From each carpet, 10 samples were left untreated, 10 vacuumed with an upright vacuum cleaner, and 10 vacuumed with a canister vacuum cleaner. Each section was then cut into 3 horizontal layers: the top 2mm, the remainder of the carpet pile, and the carpet base. The mass of Der p 1 as a proportion of carpet volume was then determined. RESULTS: The concentrations of Der p 1 in each depth layer varied considerably between the 7 untreated carpets. In the top layer, Der p 1 concentrations were (median; 25th-75th percentiles): 41.9; 28.3-92.6 pg/mm3. For the middle layer they were similar (38.1; 22.4-108.5 pg/mm3), and for the carpet base, higher (212.4; 98.8-456.2 pg/mm3). In most cases, cleaning using either type of vacuum cleaner resulted in no significant reduction in allergen concentration throughout all depth layers. A subset of carpets showed an apparent increase in Der p 1 concentration in one or more layers following vacuum cleaning. In all tests Der p 1 was collected in the vacuum cleaners' filter bags. CONCLUSIONS: The depth-distribution of Der p 1 differs widely amongst used carpets. Vacuum cleaning changes the distribution of Der p 1 within such carpets but does not necessarily result in a reduction in the overall content.

Allergens↗
PubMed2001

Quantum vacuum noise in physics and cosmology.

The concept of the vacuum in quantum field theory is a subtle one. Vacuum states have a rich and complex set of properties that produce distinctive, though usually exceedingly small, physical effects. Quantum vacuum noise is familiar in optical and electronic devices, but in this paper I wish to consider extending the discussion to systems in which gravitation, or large accelerations, are important. This leads to the prediction of vacuum friction: The quantum vacuum can act in a manner reminiscent of a viscous fluid. One result is that rapidly changing gravitational fields can create particles from the vacuum, and in turn the backreaction on the gravitational dynamics operates like a damping force. I consider such effects in early universe cosmology and the theory of quantum black holes, including the possibility that the large-scale structure of the universe might be produced by quantum vacuum noise in an early inflationary phase. I also discuss the curious phenomenon that an observer who accelerates through a quantum vacuum perceives a bath of thermal radiation closely analogous to Hawking radiation from black holes, even though an inertial observer registers no particles. The effects predicted raise very deep and unresolved issues about the nature of quantum particles, the role of the observer, and the relationship between the quantum vacuum and the concepts of information and entropy. (c) 2001 American Institute of Physics.

Journal Article↗