Browsing by Subject "VACUUM"

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  • Enqvist, Kari; Hardwick, Robert J.; Tenkanen, Tommi; Vennin, Vincent; Wands, David (2018)
    We show that in the Feebly Interacting Massive Particle (FIMP) model of Dark Matter (DM), one may express the inflationary energy scale H-* as a function of three otherwise unrelated quantities, the DM isocurvature perturbation amplitude, its mass and its self-coupling constant, independently of the tensor-to-scalar ratio. The FIMP model assumes that there exists a real scalar particle that alone constitutes the DM content of the Universe and couples to the Standard Model via a Higgs portal. We consider carefully the various astrophysical, cosmological and model constraints, accounting also for variations in inflationary dynamics and the reheating history, to derive a robust estimate for H-* that is con fined to a relatively narrow range. We point out that, within the context of the FIMP DM model, one may thus determine H-* reliably even in the absence of observable tensor perturbations.
  • Bjorck, M.; Kirkpatrick, A. W.; Cheatham, M.; Kaplan, M.; Leppäniemi, Ari; De Waele, J. J. (2016)
    Background: In 2009, a classification system for the open abdomen was introduced. The aim of such a classification is to aid the (1) description of the patient's clinical course; (2) standardization of clinical guidelines for guiding open abdomen management; and (3) facilitation of comparisons between studies and heterogeneous patient populations, thus serving as an aid in clinical research. Methods: As part of the revision of the definitions and clinical guidelines performed by the World Society of the Abdominal Compartment Syndrome, this 2009 classification system was amended following a review of experiences in teaching and research and published as part of updated consensus statements and clinical practice guidelines in 2013. Among 29 articles citing the 2009 classification system, nine were cohort studies. They were reviewed as part of the classification revision process. A total of 542 patients (mean: 60, range: 9-160) had been classified. Two problems with the previous classification system were identified: the definition of enteroatmospheric fistulae, and that an enteroatmospheric fistula was graded less severe than a frozen abdomen. Results: The following amended classification was proposed: Grade 1, without adherence between bowel and abdominal wall or fixity of the abdominal wall (lateralization), subdivided as follows: 1A, clean; 1B, contaminated; and 1C, with enteric leak. An enteric leak controlled by closure, exteriorization into a stoma, or a permanent enterocutaneous fistula is considered clean. Grade 2, developing fixation, subdivided as follows: 2A, clean; 2B, contaminated; and 2C, with enteric leak. Grade 3, frozen abdomen, subdivided as follows: 3A clean and 3B contaminated. Grade 4, an established enteroatmospheric fistula, is defined as a permanent enteric leak into the open abdomen, associated with granulation tissue. Conclusions: The authors believe that, with these changes, the requirements on a functional and dynamic classification system, useful in both research and training, will be fulfilled. We encourage future investigators to apply the system and report on its merits and constraints.
  • Rasilainen, S. K.; Mentula, P. J.; Leppaniemi, A. K. (2016)
    Background and aims: The goal after open abdomen treatment is to reach primary fascial closure. Modern negative pressure wound therapy systems are sometimes inefficient for this purpose. This retrospective chart analysis describes the use of the components separation' method in facilitating primary fascial closure after open abdomen. Material and methods: A total of 16 consecutive critically ill surgical patients treated with components separation during open abdomen management were analyzed. No patients were excluded. Results: Primary fascial closure was achieved in 75% (12/16). Components separation was performed during ongoing open abdomen treatment in 7 patients and at the time of delayed primary fascial closure in 9 patients. Of the former, 3/7 (43%) patients reached primary fascial closure, whereas all 9 patients in the latter group had successful fascial closure without major complications (p=0.019). Conclusion: Components separation is a useful method in contributing to successful primary fascial closure in patients treated for open abdomen. Best results were obtained when components separation was performed simultaneously with primary fascial closure at the end of the open abdomen treatment.
  • Kääriäinen, M.; Kuuskeri, M.; Helminen, M.; Kuokkanen, Hannu (2017)
    Background and Aims: The open abdomen technique is a standard procedure in the treatment of intra-abdominal catastrophe. Achieving primary abdominal closure within the initial hospitalization is a main objective. This study aimed to analyze the success of closure rate and the effect of negative pressure wound therapy, mesh-mediated medial traction, and component separation on the results. We present the treatment algorithm used in our institution in open abdomen situations based on these findings. Material and Methods: Open abdomen patients (n=61) treated in Tampere University Hospital from May 2005 until October 2013 were included in the study. Patient characteristics, treatment prior to closure, closure technique, and results were retrospectively collected and analyzed. The first group included patients in whom direct or bridged fascial closure was achieved, and the second group included those in whom only the skin was closed or a free skin graft was used. Background variables and variables related to surgery were compared between groups. Results and Conclusion: Most of the open abdomen patients (72.1%) underwent fascial defect repair during the primary hospitalization, and 70.5% of them underwent direct fascial closure. Negative pressure wound therapy was used as a temporary closure method for 86.9% of the patients. Negative pressure wound therapy combined with mesh-mediated medial traction resulted in the shortest open abdomen time (p=0.039) and the highest fascial repair rate (p=0.000) compared to negative pressure wound therapy only or no negative pressure wound therapy. The component separation technique was used for 11 patients; direct fascial closure was achieved in 5 and fascial repair by bridging the defect with mesh was achieved in 6. A total of 8 of 37 (21.6%) patients with mesh repair had a mesh infection. The negative pressure wound therapy combined with mesh-mediated medial traction promotes definitive fascial closure with a high closure rate and a shortened open abdomen time. The component separation technique can be used to facilitate fascial repair but it does not guarantee direct fascial closure in open abdomen patients.
  • Säde, Elina; Johansson, Per; Heinonen, Tytti; Hultman, Jenni; Björkroth, Johanna (2020)
    Lactobacillus algidus is a meat spoilage bacterium often dominating the bacterial communities on chilled, packaged meat. Yet, L. algidus strains are rarely recovered from meat, and only few studies have focused on this species. The main reason limiting detailed studies on L. algidus is related to its poor growth on the media routinely used for culturing food spoilage bacteria. Thus, our study sought to develop reliable culture media for L. algidus to enable its recovery from meat, and to allow subculturing and phenotypic analyses of the strains. We assessed the growth of meat-derived L. algidus strains on common culture media and their modifications, and explored the suitability of potential media for the recovery of L. algidus from meat. Moreover, we determined whether 12 meat-derived L. algidus strains selected from our culture collection produce biogenic amines that may compromise safety or quality of meat, and finally, sequenced de novo and annotated the genomes of two meat-derived L. algidus strains to uncover genes and metabolic pathways relevant for phenotypic traits observed. MRS agar supplemented with complex substances (peptone, meat and yeast extract, liver digest) supported the growth of L. algidus, and allowed the recovery of new L. algidus isolates from meat. However, most strains grew poorly on standard MRS agar and on general-purpose media. In MRS broth, most strains grew well but a subset of strains required supplementation of MRS broth with additional cysteine. Supplementation of MRS broth with catalase allowed growth in aerated cultures suggesting that the strains produced hydrogen peroxide when grown aerobically. The strains tested (n = 12) produced ornithine from arginine and putrescine from agmatine, and two strains produced tyramine from tyrosine. Our findings reveal that L. algidus populations are underestimated if routine culture protocols are applied, and prompt concerns that L. algidus may generate tyramine or putrescine in meat or fermented meat products.
  • Jääskeläinen, Elina; Jakobsen, Louise M.A.; Hultman, Jenni; Eggers, Nina; Bertram, Hanne C.; Björkroth, Johanna (2019)
    Microbial (colony counts, 16S rRNA gene amplification), chemical (pH, 1H NMR spectroscopy) and sensory changes in raw Atlantic Salmon (Salmo salar) and tuna (Thunnus albacares) fillets stored under vacuum at 3 °C were evaluated over a period of 12 days. Both species of fish are globally important and among the ten most consumed fishes in the world. Although the sensory analyses showed a decrease in the quality of both fish species, only the salmon fillets were considered spoiled at the end of the storage period. In salmon, trimethylamine was the main spoilage product and bacterial colony counts reached an average of 7.3 log10 cfu/g. The concentration of glucose decreased and the concentration of organic acids increased during storage revealing glucose fermentation. Photobacterium was the dominating genus in the salmon studied. In the tuna studied, the bacterial colony counts reached only an average of 4.6 log10 cfu/g. The dominating bacteria in tuna were Pseudomonas spp. Glucose levels did not decrease, suggesting that amino acids and lactate most likely acted as carbon sources for bacteria in tuna. In conclusion, the study revealed that salmon was clearly a more perishable fish than tuna.
  • Rasilainen, Suvi Kaarina; Mentula, Panu; Leppäniemi, Ari (2015)
    Introduction: This study was designed to describe the time-course and microbiology of colonization of open abdomen in critically ill surgical patients and to study its association with morbidity, mortality and specific complications of open abdomen. A retrospective cohort analysis was done. Methods: One hundred eleven consecutive patients undergoing vacuum-assisted closure with mesh as temporary abdominal closure method for open abdomen were analyzed. Microbiological samples from the open abdomen were collected. Statistical analyses were performed using Fisher's exact test for categorical variables. Mann-Whitney U test was used when comparing number of temporary abdominal closure changes between colonized and sterile patients. Kaplan-Meier analysis was done to calculate cumulative estimates for colonization. Cox regression analyses were performed to analyze risk factors for colonization. Results: Microbiological samples were obtained from 97 patients. Of these 76 (78 %) were positive. Sixty-one (80 %) patients were colonized with multiple micro-organisms and 27 (36 %) were cultured positive for candida species. The duration of open abdomen treatment adversely affected the colonization rate. Thirty-three (34 %) patients were colonized at the time of laparostomy. After one week of open abdomen treatment 69, and after two weeks 76 patients were colonized with cumulative colonization estimates of 74 % and 89 %, respectively. Primary fascial closure rate was 80 % (61/76) and 86 % (18/21) for the colonized and sterile patients, respectively. The rate of wound complications did not significantly differ between these groups. Conclusions: Microbial colonization of open abdomen is associated with the duration of open abdomen treatment. Wound complications are common after open abdomen, but colonization does not seem to have significant effect on these. The high colonization rate described herein should be taken into account when primarily sterile conditions like acute pancreatitis and aortic aneurysmal rupture are treated with open abdomen.
  • Gould, Oliver; Mangles, Stuart; Rajantie, Arttu; Rose, Steven; Xie, Cheng (2019)
    We study the possibility of observing Schwinger pair production enhanced by a thermal bath of photons. We consider the full range of temperatures and electric field intensities from pure Schwinger production to pure thermal production, and identify the most promising and interesting regimes. In particular, we identify temperatures of similar to 20 keV/k(B) and field intensities of similar to 10(23) W cm(-2) where pair production would be observable. In this case, the thermal enhancement over the Schwinger rate is exponentially large and due to effects which are not visible at any finite order in the loop expansion. Pair production in this regime can thus be described as more nonperturbative than the usual Schwinger process, which appears at one loop. Unfortunately, such high temperatures appear to be out of reach of foreseeable technologies, though nonthermal photon distributions with comparable energy densities are possible. We suggest the possibility that similar nonperturbative enhancements may extend out of equilibrium and propose an experimental scheme to test this.
  • Alanne, Tommi; Franzosi, Diogo Buarque; Frandsen, Mads T.; Kristensen, Mette L. A.; Meroni, Aurora; Rosenlyst, Martin (2018)
    We study the phenomenology of partially composite-Higgs models where electroweak symmetry breaking is dynamically induced, and the Higgs is a mixture of a composite and an elementary state. The models considered have explicit realizations in terms of gauge-Yukawa theories with new strongly interacting fermions coupled to elementary scalars and allow for a very SM-like Higgs state. We study constraints on their parameter spaces from vacuum stability and perturbativity as well as from LHC results and find that requiring vacuum stability up to the compositeness scale already imposes relevant constraints. A small part of parameter space around the classically conformal limit is stable up to the Planck scale. This is however already strongly disfavored by LHC results. In different limits, the models realize both (partially) composite-Higgs and (bosonic) technicolor models and a dynamical extension of the fundamental Goldstone-Higgs model. Therefore, they provide a general framework for exploring the phenomenology of composite dynamics.
  • Tureanu, Anca (2018)
    We formulate the quantum field theory description of neutron-antineutron oscillations in the framework of canonical quantization, in analogy with the Bardeen-Cooper-Schrieffer theory and the Nambu-Jona-Lasinio model. The physical vacuum of the theory is a condensate of pairs of would-be neutrons and antineutrons in the absence of the baryon-number violating interaction. The quantization procedure defines uniquely the mixing of massive Bogoliubov quasiparticle states that represent the neutron. In spite of not being mass eigenstates, neutron and antineutron states are defined on the physical vacuum and the oscillation formulated in asymptotic states. The exchange of the baryonic number with the vacuum condensate engenders what may be observed as neutron-antineutron oscillation. The convergence between the present canonical approach and the Lagrangian/path integral approach to neutron oscillations is shown by the calculation of the anomalous (baryon-number violating) propagators. The quantization procedure proposed here can be extended to neutrino oscillations and, in general, to any particle oscillations.
  • Kupiainen, Tomi; Tureanu, Anca (2021)
    We present a prescription for consistently constructing non-Fock coherent flavour neutrino states within the framework of the seesaw mechanism, and establish that the physical vacuum of massive neutrinos is a condensate of Standard Model massless neutrino states. The coherent states, involving a finite number of massive states, are derived by constructing their creation operator. This construction fulfills automatically the key requirement of coherence for the oscillations of particles to occur. We comment on the inherent non-unitarity of the oscillation probability induced by the requirement of coherence.
  • Rasilainen, Suvi; Mentula, Panu; Salminen, Paulina; Koivukangas, Vesa; Hyöty, Marja; Mäntymäki, Leena-Mari; Pinta, Tarja; Haikonen, Jyrki; Rintala, Jukka; Rantanen, Tuomo; Strander, Tapani; Leppäniemi, Ari (2020)
    BACKGROUND Open abdomen (OA) is a useful option for treatment strategy in many acute abdominal catastrophes. A number of temporary abdominal closure (TAC) methods are used with limited number of comparative studies. The present study was done to examine risk factors for failed delayed primary fascial closure (DPFC) and risk factors for mortality in patients treated with OA. METHODS This study was a multicenter retrospective analysis of the hospital records of all consecutive patients treated with OA during the years 2009 to 2016 at five tertiary referral hospitals and three secondary referral centers in Finland. RESULTS Six hundred seventy-six patients treated with OA were included in the study. Vacuum-assisted closure with continuous mesh-mediated fascial traction (VACM) was the most popular TAC method used (N = 398, 59%) followed by VAC (N = 128, 19%), Bogota bag (N = 128, 19%), and self-designed methods (N = 22, 3%). In multivariate analysis, enteroatmospheric fistula and the number of needed TAC changes increased the risk for failed DPFC (odds ratio [OR], 8.9; 95% confidence interval [CI], 6.2-12.8; p <0.001 and OR, 1.1; 95% CI, 1.0-1.3; p <0.001, respectively). Instead, VACM and ruptured abdominal aortic aneurysm as cause for OA both decreased the risk for failed DPFC (OR, 0.1; 95% CI, 0.0-0.3; p <0.001 and OR, 0.2; 95% CI, 0.1-0.7; p = 0.012). The overall mortality rate was 30%. In multivariate analysis for mortality, multiorgan dysfunction (OR, 2.4; 95% CI, 1.6-3.6; p <0.001), and increasing age (OR, 4.5; 95% CI, 2.0-9.7; p <0.001) predicted increased mortality. Institutional large annual patient volume (OR, 0.4; 95% CI, 0.3-0.6; p <0.001) and ileus and postoperative peritonitis in comparison to severe acute pancreatitis associated with decreased mortality (OR, 0.2; 95% CI, 0.1-0.4; p <0.001; OR, 0.5; 95% CI, 0.3-0.8; p = 0.009). Kaplan-Meier analysis showed increased survival in patients treated with VACM in comparison with other TAC methods (LogRank p = 0.019). CONCLUSION We report superior role for VACM methodology in terms of successful primary fascial closure and increased survival in patients with OA.