In vivo quantification of the 3D kinematics and coupling of the thumb base joints.

Full thumb mobility is required to execute tasks of daily living and results from the combined motions of the thumb joints. In this study, we focus on the coupling between the proximal joints of the thumb, the radioscaphoid (RS), scaphotrapezial (ST) and trapeziometacarpal (TMC) joints. We quantified the 3D kinematics of these joints during maximal thumb extension and abduction in a group of healthy volunteers using an image-based technique. Semi-dynamic CT scans of the dominant hand of 36 healthy subjects with the thumb in different standardized positions were used. The maximal range of motion of each joint in the different planes was calculated using a markerless bone registration method. Inter-joint coupling was assessed by performing a regression analysis between the range of motion of the joints during both thumb movements. Strong inter-joint coupling was found between the RS and ST joints during thumb extension and abduction, whereas coupling between the other joints was moderate to weak. This study provides valuable information on the in vivo 3D kinematics of the RS, ST and TMC joints during thumb movement. This can be used as input for modeling studies, where the coupling between the joints can decrease the degrees of freedom of the model. Moreover, these baseline data of a healthy cohort can be used for comparison with the kinematics of patients with TMC osteoarthritis or other pathologies and aid our understanding of motion deficits resulting from these joint disorders.

Anatomy and biomechanics of healthy and arthritic trapeziometacarpal joints.

Understanding the biomechanics of the trapeziometacarpal (TMC) or first carpometacarpal (CMC1) joint, the pathophysiology of basal thumb arthritis, the design and performance of surgical procedures require a solid anatomical basis. This review of literature summarizes the most recent data on the descriptive, functional, and comparative anatomy of healthy and arthritic TMC joints.

Quantifying thumb opposition kinematics using dynamic computed tomography.

Current motion capture techniques all have shortcomings when applied to the 3D quantitative evaluation of thumb base motion. Dynamic CT might overcome these shortcomings but, so far, robustness of this technique in more than one specimen has not yet been demonstrated. The aim of the current study is to further evaluate the use of dynamic CT for quantification of thumb motion in a larger cadaveric study using a protocol which is feasible in a clinical context. A dynamic CT scan was acquired from six cadaveric human forearms, while a motion simulator imposed thumb opposition. After image acquisition and segmentation, carpal bone motion was quantified using helical axes. To enable comparisons between specimens, intersection points of the instantaneous helical axis with an anatomically defined plane were determined. Precision of the dynamic CT method, measured as variation in distances between silicon nitride beads between frames of a dynamic scan, was 0.43mm (+/-0.09mm) when fixed to the skin and 0.13mm (+/-0.04mm) when embedded into the bone. Absolute deviation between known and measured distances were not larger than 0.34mm. We could demonstrate and quantify that thumb opposition is associated with motion at the trapeziometacarpal and scaphotrapezotrapezoidal joints. High consistency in motion patterns between specimen were found, while the radiation dose was limited. We conclude that dynamic CT can be used to visualize and quantify 3D thumb kinematics, making it a promising method to explore kinematics in vivo.

Comparison of the anatomical dimensions and mechanical properties of the dorsoradial and anterior oblique ligaments of the trapeziometacarpal joint.

PURPOSE: The respective roles of the dorsoradial (DRL) and anterior oblique (AOL) ligaments in stability of the highly mobile trapeziometacarpal (TMC) joint remain disputed. Earlier publications have pointed to the AOL as the key stabilizing structure; yet, more recent publications have challenged the stabilizing role of the AOL, favoring the DRL as the main TMC joint stabilizer. We executed an anatomical study of the ligaments, including detailed dissection to quantify the length, width, and thickness of the AOL and DRL and tested the material properties of these ligaments. METHODS: Thirteen fresh frozen cadaveric thumbs from 9 specimens were used. Length, width, and thickness of the AOL and DRL were measured on magnetic resonance imaging and/or after dissection. Next, the first metacarpal and trapezium were isolated together with both ligaments, and both bones were cut sagittally to isolate a first metacarpal-AOL-trapezium and first metacarpal-DRL-trapezium complex from each thumb. These samples were subjected to cyclic loading in displacement-controlled tests. The obtained force-displacement curves were used to calculate stiffness and hysteresis of each sample. RESULTS: Our results showed that the DRL is significantly shorter and thicker than the AOL, which is thin and ill-defined. Our results also indicate that the DRL has a higher stiffness than the AOL, making it a more likely candidate to provide joint stability. CONCLUSIONS: Although the AOL has been asserted to be the primary restraint to dorsoradial subluxation, this view has been challenged over the past 10 years by several studies. These studies have shown the AOL to be relatively weak and compliant compared with the intermetacarpal and dorsoradial ligaments and have demonstrated that the DRL is the strongest and stiffest ligament of the TMC joint. Our studies confirm these findings. CLINICAL RELEVANCE: This study indicates that the DRL is relatively stiff and thick, suggesting it should be repaired or reconstructed when disrupted to restore stability of the TMC joint.

An investigation of the effect of AlloMatrix bone graft in distal radial fracture: a prospective randomised controlled clinical trial.

The osteoinductive properties of demineralised bone matrix have been demonstrated in animal studies. However, its therapeutic efficacy has yet to be proven in humans. The clinical properties of AlloMatrix, an injectable calcium-based demineralised bone matrix allograft, were studied in a prospective randomised study of 50 patients with an isolated unstable distal radial fracture treated by reduction and Kirschner (K-) wire fixation. A total of 24 patients were randomised to the graft group (13 men and 11 women, mean age 42.3 years (20 to 62)) and 26 to the no graft group (8 men and 18 women, mean age 45.0 years (17 to 69)). At one, three, six and nine weeks, and six and 12 months post-operatively, patients underwent radiological evaluation, assessments for range of movement, grip and pinch strength, and also completed the Disabilities of Arm, Shoulder and Hand questionnaire. At one and six weeks and one year post-operatively, bone mineral density evaluations of both wrists were performed. No significant difference in wrist function and speed of recovery, rate of union, complications or bone mineral density was found between the two groups. The operating time was significantly higher in the graft group (p = 0.004). Radiologically, the reduction parameters remained similar in the two groups and all AlloMatrix extraosseous leakages disappeared after nine weeks. This prospective randomised controlled trial did not demonstrate a beneficial effect of AlloMatrix demineralised bone matrix in the treatment of this category of distal radial fractures treated by K-wire fixation.

Liquid chromatography electrospray tandem mass spectrometric and desorption electrospray ionization tandem mass spectrometric analysis of chemical warfare agents in office media typically collected during a forensic investigation.

Most prior analytical studies have dealt with the determination of chemical warfare agents in environmental or biological matrices that would typically be collected following battlefield use or in support of the Chemical Weapons Convention. These methods may be useful for some investigations, but may not be practical for indoor forensic investigations where chemical warfare agent use is suspected. There is a need for analytical methods for chemical warfare agent identification in office media, including flooring, wall surfaces, office fabrics and paper products, which would typically be collected in an office environment during forensic investigations. During this study, typical office environment media were spiked at the 4-20microg/g level with either a complex munitions grade sample of tabun (GA) or with a standard containing the three nerve agents, sarin (GB), cyclohexyl methylphosphonofluoridate (GF), soman (GD) and the nerve agent simulant, triethyl phosphate (TEP), to evaluate the potentials of liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS) and liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) for forensic purposes. An emerging technique, desorption electrospray ionization (DESI-MS/MS), was also investigated for the direct determination of TEP, GB and GD sampled onto solid phase microextraction (SPME) fibers exposed to spiked office media. The spiked chemical warfare agents were recovered with varying efficiencies during this study, but in all cases sufficient chemical warfare agent was recovered for mass spectrometric identification purposes. Full high resolution mass spectra were acquired for all the chemical warfare agents in the continuum mode, which typically resulted in mass measurement errors of 0.001Da or less.

Production of cytokines at the operation site.

BACKGROUND AND AIM: Cytokines are part of a family of molecules involved in the initiation, control and termination of the events that occurs in wound healing process. Aim of this study was to evaluate the production of some cytokines [interleukin (IL)-6, IL-10, IL-1alpha, IL-1ra, interferon (IFN)-gamma] in the drainage wound fluid from patients undergoing incisional hernia repair. METHODS: Ten female patients with abdominal midline incisional hernia undergoing to surgical repair were included in this study. In all cases a closed suction drain was placed in the wound below the fascia and it was removed on the 4th postoperative day. Wound fluid was collected on the 1st, 2nd, 3rd and 4th day and its amount in each time was recorded. The production of IL-6, IL-10, IL-1alpha, IL-1ra and IFN-gamma were evaluated as quantity produced in 24 hour. RESULTS: In all patients the amount of drain fluid from surgical wound was highest on the 1st day after surgery, afterwards there is a significant reduction. The production of all cytokines evaluated was highest on the 1st day decreasing on the 2nd day except for IL-1alpha that not show any modification. The produciton of IL-1ra, IL-6, IL-1alpha and IL-10 was significantly reduced on the 3rd and 4th postoperative day in comparison with the respectively values recorded on the 1st day, whereas IFN-gamma levels were similar. CONCLUSIONS: The dosage of cytokines in the drain fluid led us to better evaluated the events that follow surgical wound and their analysis offers further information in the role of cytokines in healing process, with the goal to get supportive treatments to promote the best evolution.

Risk management: medical malpractice and Emergency Department.

Because of the limited number of comprehensive paediatric centres, providing the entire continuum of paediatric care, including subspecialty care, and generally serving as regional referral centres for tertiary paediatrics, paediatric emergency care in Italy is often provided in adult facilities within primarily adult hospital institutions. Consequently, most paediatricians working in hospitals with a separate paediatric ward or department provide Emergency Department (ED) on-call coverage with serious liability concerns: such concerns are due to the fact that successful care of infants and children in an emergency situation requires appropriately sized equipment, well trained staff, appropriate and specialised triage and destination guidelines but, unfortunately, not all Italian facilities fulfil all these criteria. Risk management training of the entire ED staff may reduce the institution's involvement in malpractice litigation. Another useful tool within a paediatric ED is an Observation Unit (OU) for well-defined illnesses (such as asthma, croup, bronchiolitis, gastroenteritis, abdominal pain, mild dehydration, overdoses or poisoning, seizures), which can assure better patient's care, a decrease in missed diagnosis and acuity and decreased lenght of stay, and, consequently, a better risk management, decreased malpractice liability and cost effectiveness. Furthermore, in our paper we aimed to highlight the importance of aspects with a potential risk exposure in our profession, such as informed consent, exculpatory release forms, incident reports and complete ED record documentation of paediatric patients. In addition to that, the quality of care provided at ED in Italy has been assessed by analysing ED-related paediatric malpractice claims in the last 10 years. Finally, the importance of a joint commission within the Italian Paediatrics Society is underlined in order to discuss practice guidelines for paediatricians involved in emergency care.

Interleukin-15, as interferon-gamma, induces the killing of Leishmania infantum in phorbol-myristate-acetate-activated macrophages increasing interleukin-12.

The potential leishmanicidal activity of interleukin-15 (IL-15) was examined while priming with the cytokine phorbol-myristate-acetate (PMA)-activated macrophages and infecting them with Leishmania infantum parasites. The activation of macrophage cultures with IL-15 determined a significant anti-leishmanial activity, comparable with that induced by interferon-gamma (IFN-gamma). The killing of Leishmania in macrophages primed with IL-15, as well as with IFN-gamma, was followed by an increase in the IL-12 synthesis. The neutralization of IL-15 or IFN-gamma, by specific monoclonal antibodies (MoAb) caused a significant reduction in leishmanicidal activity. Furthermore, in PMA-activated macrophages, the neutralization of IL-12 production by a specific anti-IL-12 MoAb reduced leishmanicidal activity induced by IL-15 and IFN-gamma. Data indicate that IL-15 could have a role as an activator of leishmanicidal activity, directly or indirectly, by inducing IL-12 production.

Packed capillary liquid chromatography-electrospray ionization (tandem) mass spectrometry of mustard hydrolysis products in soil.

A packed capillary liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) method was developed and applied to the identification of mustard hydrolysis products in aqueous extracts of soil. In the first application the LC-ESI-MS/MS method was used to identify thiodiglycol and nine longer chain diols in soil samples taken at different locations and depths from a former mustard storage site as part of an ongoing environmental assessment. Aqueous extracts of the soil samples were analysed by LC-ESI-MS/MS using a quadrupole/time-of-flight tandem mass spectrometer operating with a resolution of 9000. High resolution product mass spectra were acquired for thiodiglycol, the hydrolysis product of mustard and nine other sulfur containing diols, including five longer chain diols that could not be identified during prior LC-ESI-MS analyses. The high resolution LC-ESI-MS/MS method was also incorporated into an analytical approach designed to provide rapid chemical warfare agent identification in cases where the chemical and/or biological warfare agent content of a sample is unknown. A sample handling method involving aqueous extraction of the soil sample in biocontainment level 3 (BL-3), followed by autoclave sterilization of the aqueous extract was developed. Once sterilized, the container and aqueous extract can then be safely manipulated outside of BL-3 in the analytical laboratories and may be analysed for the presence or absence of chemical warfare agents, their hydrolysis products or related compounds by LC-ESI-MS/MS.

Matrix metalloproteinases production in malignant pleural effusions after talc pleurodesis.

In this study we have evaluated the modifications of matrix metalloproteinases (MMPs) in malignant pleural fluids taken from patients suffering from lung cancer and treated with intrapleural talc instillation to induce pleurodesis. Furthermore, we have analysed the variations of some inflammatory mediators (C-reactive protein, alpha-1 antitrypsin) and of a protein (plasminogen) involved in MMP activation. In all patients the clinical improvement after talc pleurodesis was followed by a reduction in MMP-1, TIMP-1, C-reactive protein, alpha-1 antitrypsin and plasminogen activity. Furthermore, MMP-9 levels were variable; in fact, in some patients they were high at the beginning of treatment, in others they increased a few days after pleurodesis induction. These inhibitory effects of talc on MMP-1 and inflammatory mediators associated with the reduction of pleural effusion could constitute an effective means to evaluate the evolution of the treatment.

Packed capillary liquid chromatography-electrospray mass spectrometry of snow contaminated with sarin.

Packed capillary liquid chromatography-electrospray mass spectrometry (LC-ESI-MS) was used for the analysis of a snow sample that was accidentally contaminated with an organophosphorus chemical warfare agent during the destruction of a chemical munition. Sarin, its hydrolysis products and a number of related compounds were identified on the basis of acquired LC-ESI-MS data. Full mass spectra were acquired for 14 compounds, with all exhibiting MH+, [MH+ACN]+ ions and/or protonated dimers that could be used to confirm molecular mass. Sampling cone voltages from 20 to 70 V were utilized with the higher sampling voltages enhancing formation of structurally important product ions in the ESI interface. All data were acquired with a time-of-flight mass spectrometer with a resolution of 5,000 (50% valley definition), a resolution that aided in the assignment of elemental composition of the observed ions. The application of LC-ESI-MS to snow analysis appears to be an attractive alternative to the GC-MS methods, since both chemical warfare agents and their hydrolysis products may be analysed directly, eliminating the need for additional sample handling and derivatization steps.

IL-15 in human visceral leishmaniasis caused by Leishmania infantum.

Interleukin (IL)-15 is a recently discovered cytokine with the ability to stimulate the proliferation activity of Th1 and/or Th2 lymphocytes. Here, we investigated the involvement of IL-15 in the immune response to Leishmania infantum infection by studying patients with visceral leishmaniasis (VL). We found that IL-15 is produced by leishmanial antigen (LAg)-stimulated peripheral blood mononuclear cells (PBMC) from active VL patients at a significantly higher level than those produced by cells from healed VL subjects or healthy controls. A significant increase in IL-15 serum blood levels was also observed in acute VL patients compared with healed ones. Furthermore, recombinant IL-15 had an appreciable effect in vitro in reducing IL-4 and increasing the production of IL-12 in response to LAg, but it was ineffective in altering the production of interferon-gamma (IFN-gamma). The production of endogenous IL-15 in acute VL patients appeared to be insufficient to activate both IFN-gamma and IL-12, as attested by the absence of modification of these two cytokines by neutralization experiments in the presence of anti-IL-15 monoclonal antibodies (MoAB). On the contrary, the neutralization of IL-15 increased IL-4 production. Together, these results indicate that endogenous IL-15 plays a role in the suppression of Th2-type cytokines, even though it does not enhance the production of Th1 cytokines in acute VL patients. Since IL-15, in the presence of anti-IL-4 MoAb, caused a further increase in IL-12 production and led to a significant production of IFN-gamma, one of its indirect effects on Th1 cell activation could be due to the latter's effect on Th2 cytokines such as IL-4. Therefore, our observations indicate that there is a potential for IL-15 to augment the T-cell response to human intracellular pathogens.

Anti-inflammatory effects of chemically modified tetracyclines by the inhibition of nitric oxide and interleukin-12 synthesis in J774 cell line.

We investigated the effects of chemically modified tetracyclines (CMTs) on the production of nitric oxide (NO) and on the synthesis of some cytokines: tumour necrosis factor alpha (TNF-alpha), interleukin(IL)-10 and IL-12 in lipopolysaccharide (LPS)-treated J774 cell line. Furthermore, we studied the ability of these drugs to modify the viability in LPS-stimulated J774 macrophages. CMTs decreased, in a dose-dependent manner, inducible NO synthase (iNOS) activity and, consequently, nitrite formation in J774 cultures. The CMT-induced decrease in NO production is due to the inhibition of enzyme activity rather than to a direct effect on enzyme expression. The absence of the inhibition in mRNA accumulation indicates that the inhibiting activity is mainly post-transcriptional. CMTs were unable to modulate TNF-alpha and IL-10 synthesis and they were not effective in modifying the transcription of relative mRNA in J774 macrophages. On the contrary, IL-12 mRNA expression was significantly increased by CMT-1 and CMT-8 with LPS activation. Since IL-12 protein secretion was inhibited by CMTs, these compounds interfere in the blocking of post-transcriptional events. The studies on cell viability showed that various CMTs induced a dose-dependent decrease in J774 macrophage viability. The cytotoxic activity was present even though NO production was inhibited by CMTs. These compounds appear to be able to activate apoptosis in aNO-independent way. Altogether, these results indicate that CMTs can exert anti-inflammatory effects by inhibiting NO synthesis, and they are able to modify cell viability by exerting a strong apoptotic activity.

Cytokine modifications after tension-free hernioplasty or open conventional inguinal hernia repair.

BACKGROUND: The purpose of this study was to evaluate the involvement of proinflammatory cytokines (interferon-gamma [INF-gamma], interleukin [IL]-6) and anti-inflammatory cytokines (IL-4, IL-l0, IL-13) in patients undergoing Lichtenstein tension-free hernioplasty (LH) using polypropylene prosthetic materials or conventional Bassini hernia (BH) repair. METHODS: Thirty-five male patients (age range 25 to 60 years) with unilateral inguinal hernia without complications or recurrence were included in this study. Randomly, patients underwent conventional operation and had their inguinal hernia repair performed with polypropylene mesh. Peripheral venous blood samples were collected 24 hours prior to surgery and then 6, 24, 48, and 168 hours postoperatively. Fifteen healthy controls were included. RESULTS: We present evidence that LH patients showed both an increased serum level of Thelper 1 (Th1)-like cytokines (IFN-gamma) and an increase in Thelper 2 (Th2)-like cytokines (IL-6 and IL-l0), associated with a slight reduction of peripheral blood mononuclear cells (PBMC) producing IL-6 and a normal level of PBMC producing IFN-gamma, IL-l0, IL-13, and IL-4. Whereas BH patients showed in part an amplification of Th2-like cells, characterized by the sustained serum production of IL-6 and IL-l0, associated with an increase in IL-l0 secreted by in vitro stimulated PMBC. CONCLUSIONS: Our data show that LH is associated with a higher production of inflammatory cytokines (IFN-gamma and IL-6) compared with BH, likely induced by the presence of the polypropylene prostheses.

Determination of sarin, soman and their hydrolysis products in soil by packed capillary liquid chromatography-electrospray mass spectrometry.

An analytical method based on aqueous ultrasonic extraction and packed capillary liquid chromatography-electrospray mass spectrometry (LC-ESI-MS) analysis was developed and compared to an existing gas chromatography(GC)-MS based method for the determination of sarin, soman and their hydrolysis products in contaminated soil. Three soils, a red clay, a tan sandy clay and a brown sandy clay loam, were spiked with sarin and soman and their initial hydrolysis products, isopropyl methylphosphonic acid and pinacolyl methylphosphonic acid, at the 10 microg/g level to assess recovery efficiency. Recovery of sarin and soman from the aqueous soil extracts was comparable to the existing analytical method, with a significant improvement in recovery being demonstrated for the chemical warfare agent hydrolysis products. Sarin and soman were recovered in the 20-90% range from the three soil types with aqueous extraction, while the hydrolysis products of these chemical warfare agents were extracted with recoveries in excess of 80%. The developed soil extraction and analysis method appears to be an attractive alternative to the GC-MS based method, since aqueous extracts containing chemical warfare agent hydrolysis products may be analysed directly, eliminating the need for additional sample handling and derivatization steps.

Effects of chemically modified tetracyclines (CMTs) in sensitive, multidrug resistant and apoptosis resistant leukaemia cell lines.

Recently discovered chemically modified tetracyclines (CMTs) have shown in vitro and in vivo anti-proliferative and anti-tumour activities. Here, we evaluated in vitro the anti-proliferative and apoptotic activity of six different dedimethylamino chemically modified tetracyclines (CMT-1, CMT-3, CMT-5, CMT-6, CMT-7 and CMT-8) in sensitive and multidrug resistant myeloid leukaemia cells (HL60 and HL60R) in vitro. Three of these compounds (CMT-5, CMT-6, CMT-7) showed low cytotoxic activity both in sensitive and in resistant cells, CMT-3 was endowed with a high anti-proliferative activity only in sensitive cells and was moderately effective as apoptosis inducing agent, with an activity similar to that shown by doxycycline. On the contrary, CMT-1 and CMT-8 were very effective as programmed cell death inducing agents. The apoptotic pathway activated by these compounds involved the activation of caspases, especially caspase-9 and, for CMT-1, also the activation of FAS: Interestingly CMT-8, but not CMT-1, was able to induce apoptosis in multidrug resistant HL60R and in Fas-ligand resistant HUT78B1 cell lines. These properties, together with others previously described (e.g. anti-metastatic and anti-osteolytic activities), suggest that CMT-8 may have important applications in the clinical management of cancer. The comparative analysis of structure-activity relationship of CMT-8 and doxycycline suggests that the C-5 hydroxy moiety may play an important role in conferring activity in multidrug resistant cells. These findings appear to support the hypothesis that CMT-8 may represent an interesting lead for the development of a new class of potent apoptosis inducer agents active in multidrug resistant and Fas-ligand resistant malignancies.

The acute phase response in Sicilian patients with boutonneuse fever admitted to hospitals in Palermo, 1992-1997.

OBJECTIVES: To study the modifications of some components of the acute phase response (APR) in Sicilian patients with boutonneuse fever (BF) caused by Rickettsia conorii. METHODS: Sera from 500 Sicilian patients with confirmed BF were studied at the time of diagnosis and every week after treatment, and after recovery for the presence of various inflammatory mediators. Tumour necrosis factor alpha (TNFalpha), interleukin(IL)-6, IL-1alpha, IL-8, soluble TNF receptors (sTNF-R) and sIL-6R were assayed by commercially ELISA kits. C3, C4, factor B, C-reactive protein (CRP), fibrinogen, ceruloplasmin (Cp) and alpha(1)-antitrypsin (AAT) were assayed by a rate nephelometry. RESULTS: Interferon gamma (IFNgamma), IL-6, TNFalpha, and IL-10 cytokines were significantly modified, whereas IL-1 and IL-8 were not detectable in the blood in any phase of infection. sTNF-RI, sTNF-RII and sIL-6 were significantly increased in the first 2 weeks of infection, but sTNF-R levels were not related to the plasma levels of TNFalpha, whereas sIL-6 was directly related to serum IL-6 concentrations. C3, C4, factor B and CRP were significantly increased in the first 2 weeks of infection, but afterwards returned to the normal range, even though CRP was still high in the third week and C3 persisted high after the fourth week. Fibrinogen was high only in the first week in relation to the injury to the endothelial cells (ECs). The anti-inflammatory proteins, Cp and AAT, were extremely high in the first 2 weeks of infection acting as a buffer of APR activation. CONCLUSIONS: These results suggest that R. conorii is able to elicit, after invasion and proliferation in the ECs, the activation of APR. Further work is required to establish if active inhibitory mechanisms are operating during APR, or if there is a spontaneous decay in the initiation events.