Temperature dependence of Rb 5P fine-structure transfer induced by 4He collisions.

Employing ultrafast laser excitation and time-correlated single-photon counting, we have measured the fine-structure transfer between Rb 5P states induced by collisions with 4He buffer gas at temperatures up to 150 °C. The temperature dependence of the binary cross section agrees with earlier measurements. Our data show that the temperature dependence of the three-body rate is about the same as that of the binary rate. The three-body rate can be described as arising from the reduction of the rubidium fine-structure splitting due to nearby helium atoms.

COVID-19 via intrauterine transmission in a critically ill preterm infant: A case report.

A preterm infant was born emergently at 29 weeks gestation to a mother with active coronavirus disease 2019 (COVID-19). Clinical presentation and evaluation were consistent with in utero transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The neonate experienced progressive, refractory respiratory failure and catastrophic intracranial hemorrhage which ultimately led to limitation of care.

Enhancement of Rb fine-structure transfer in 4He due to three-body collisions.

Using ultrafast laser excitation and time-correlated single-photon counting techniques, we have measured the collisional mixing rates between the rubidium 5(2)P fine-structure levels in the presence of (4)He gas. A nonlinear dependence of the mixing rate with (4)He density is observed. We find Rb fine-structure transfer is primarily due to binary collisions at (4)He densities of < or = 10(19) cm(-3), while at greater densities, three-body collisions become significant. We determine a three-body collisional transfer rate coefficient (5(2)P(3/2) --> 5(2)P(1/2)) of 1.25(9)x10(-32) cm(6)/s at 22 degrees C.

Observation of persistent species temperature separation in inertial confinement fusion mixtures.

The injection and mixing of contaminant mass into the fuel in inertial confinement fusion (ICF) implosions is a primary factor preventing ignition. ICF experiments have recently achieved an alpha-heating regime, in which fusion self-heating is the dominant source of yield, by reducing the susceptibility of implosions to instabilities that inject this mass. We report the results of unique separated reactants implosion experiments studying pre-mixed contaminant as well as detailed high-resolution three-dimensional simulations that are in good agreement with experiments. At conditions relevant to mixing regions in high-yield implosions, we observe persistent chunks of contaminant that do not achieve thermal equilibrium with the fuel throughout the burn phase. The assumption of thermal equilibrium is made in nearly all computational ICF modeling and methods used to infer levels of contaminant from experiments. We estimate that these methods may underestimate the amount of contaminant by a factor of two or more.

Benzotriazole and 5-methylbenzotriazole in recycled water, surface water and dishwashing detergents from Perth, Western Australia: analytical method development and application.

A simplified and sensitive liquid chromatography mass spectrometry (LC-MS) method without requiring sample pre-concentration was successfully developed for detecting the occurrence of ultra-low (ng L(-1)) concentrations of benzotriazole (BTri), and its derivative 5-methyl benzotriazole (5-MeBT) in various Western Australian environmental water samples. The method detection limit was 2 ng L(-1), providing similar detection limits to other more process intensive methods where pre-concentration using solid phase extraction (SPE) was employed. The method was used to assess the occurrence of BTri and 5-MeBT in wastewater and surface water samples. Over a period of 12 months, BTri and 5-MeBT concentrations in secondary treated wastewater were measured, with the highest BTri and 5-MeBT concentrations observed during winter months at 78 ng L(-1) and 21 ng L(-1), respectively. The method was also used to assess the removal efficiency of BTri and 5-MeBT through an advanced water recycling plant (AWRP). While BTri was more persistent than 5-MeBT, both compounds were removed from the AWRP to <10 ng L(-1) (BTri) and <2 ng L(-1) (5-MeBT), with reverse osmosis (RO) providing the most effective treatment process for their removal.

Fate of benzotriazole and 5-methylbenzotriazole in recycled water recharged into an anaerobic aquifer: column studies.

The fate of benzotriazole (BTri) and 5-methylbenzotriazole (5-MeBT) was investigated under anaerobic conditions at nano gram per litre concentrations in large-scale laboratory columns to mimic a managed aquifer recharge replenishment strategy in Western Australia. Investigations of BTri and 5-MeBT sorption behaviour demonstrated mobility of the compounds with retardation coefficients of 2.0 and 2.2, respectively. Degradation processes over a period of 220 days indicated first order biodegradation of the BTri and 5-MeBT under anaerobic aquifer conditions after a biological lag-time of approximately 30-60 days. Biodegradation half-lives of 29 ± 2 and 26 ± 1 days for BTri and 5-MeBT were respectively observed, with no threshold effect to biodegradation observed at the 200 ng L(-1). The detection of degradation products provided further evidence of BTri and 5-MeBT biodegradation. These results suggested that if BTri and 5-MeBT were present in recycled water recharged to the Leederville aquifer, biodegradation during aquifer passage is likely given sufficient aquifer residence times or travel distances between recycled water injection and groundwater extraction.

Pathoanatomy of intra-articular fractures of the calcaneus.

Radiographs of 220 calcaneal fractures (205 patients) were reviewed retrospectively. One hundred and sixty-three fractures were intra-articular; thirty (18 per cent) of the 163 fractures were a tongue-type injury, and 133 (82 per cent) were a joint-depression injury. Plain radiographs and computerized tomography scans in the coronal and axial planes were available for 116 intra-articular fractures (106 patients). These studies were reviewed, and the 116 fractures were grouped according to the Sanders classification of calcaneal fractures and the anterior extension of the primary fracture line was evaluated. Sixty-two primary fracture lines (53 per cent) extended into one articular surface; twenty-three (20 per cent), into two articular surfaces; twenty-three (20 per cent), into a periarticular location; and eight (7 per cent), into a medial or lateral location. Sixty-seven (58 per cent) involved the calcaneocuboid joint, thirty-one (27 per cent) involved the anterior facet of the talocalcaneal joint, and ten (9 per cent) involved the middle facet of the talocalcaneal joint. A distinct anterolateral fragment was identified in 108 fractures (93 per cent). Plain radiographs failed to demonstrate the anterior extension of fifty-one (47 per cent) of the primary fracture lines. The prevalence of involvement of the anterior facet was significantly greater in Sanders type-III fractures (sixteen of thirty-five; 46 per cent) than in the other types (p < 0.01). The prevalence of involvement of the calcaneocuboid joint and the middle facet was evenly distributed among the fracture types. The primary fracture line typically extends anterior to the angle of Gissane, creating a relatively consistent anterolateral fracture fragment. The primary fracture line cannot be reliably seen on plain radiographs and is better visualized on computerized tomographic scans.

Complications of heparin therapy after total joint arthroplasty.

The cases of 112 patients who were treated intravenously with heparin for thromboembolic disease after total joint arthroplasty were reviewed. The over-all frequency of bleeding complications that were associated with therapy with heparin was approximately 30 per cent. In patients who were treated within six days after total joint replacement, the frequency of bleeding complications was 45 per cent. The prevalence of bleeding problems declined to 15 per cent in patients who were treated more than one week after arthroplasty. In roughly 35 per cent of the patients, therapy with heparin had to be discontinued because of complications. Thrombocytopenia developed in fewer than 5 per cent of the patients. It was concluded that anticoagulation therapy with heparin for clinically unimportant thromboembolic problems in the immediate postoperative period is not justified.

Cardiac arrest during hip arthroplasty with a cemented long-stem component. A report of seven cases.

Seven patients had a cardiac arrest during hip arthroplasty with a cemented long-stem femoral component. Four patients died in the operating room, and three patients were successfully resuscitated. When the three survivors were eventually discharged from the hospital, they had no known permanent cardiac, pulmonary, or neurological sequelae. Factors that were common to all of the patients were advanced age, osteoporotic bone, a previously undisturbed intramedullary canal, and use of a long-stem femoral component and several batches of methylmethacrylate. Hip arthroplasty with a long-stem femoral component is associated with substantial risk in these patients. Excessive pressurization of cement should be avoided, and invasive hemodynamic monitoring should be used when the described conditions are present.

Protein depletion and metabolic stress in elderly patients who have a fracture of the hip.

A prospective study was performed to determine the effect of protein depletion and postoperative nutritional status on the outcome in sixty-three elderly patients who had been admitted to the hospital because of a fracture of the hip. The parameters that were used to determine the degree of protein depletion included levels of albumin, of prealbumin, and of transferrin; total lymphocyte count; and nitrogen-balance studies. The outcomes that were examined were the development of complications, the length of the stay in the hospital, the ability to return to the pre-fracture level of function, and over-all survivorship. The hypothesis was that the acute fracture and the subsequent operation are severe stresses in these elderly, often compromised patients. The results supported the hypothesis. Thirty-seven patients (58 per cent) in the study group were in a protein-depleted state during the period of hospitalization. The patients who were protein-depleted had a higher prevalence of complications, were less likely to return to their pre-fracture environment, and tended to stay in the hospital longer, as compared with the nonprotein-depleted patients. Survivorship analysis showed that protein-depleted patients had a significantly lower probability of survival one year after the fracture of the hip (p = 0.02). Elderly patients who sustain the trauma of a fracture of the hip should be managed appropriately with regard to intake of nutrients in the postoperative period.

A prospective evaluation of the clinical utility of the lower-extremity injury-severity scores.

BACKGROUND: High-energy trauma to the lower extremity presents challenges with regard to reconstruction and rehabilitation. Failed efforts at limb salvage are associated with increased patient mortality and high hospital costs. Lower-extremity injury-severity scoring systems were developed to assist the surgical team with the initial decision to amputate or salvage a limb. The purpose of the present study was to prospectively evaluate the clinical utility of five lower-extremity injury-severity scoring systems. METHODS: Five hundred and fifty-six high-energy lower-extremity injuries were prospectively evaluated with use of five injury-severity scoring systems for lower-extremity trauma designed to assist in the decision-making process for the care of patients with such injuries. Four hundred and seven limbs remained in the salvage pathway six months after the injury. The sensitivity, specificity, and area under the receiver operating characteristic curve were calculated for the Mangled Extremity Severity Score (MESS); the Limb Salvage Index (LSI); the Predictive Salvage Index (PSI); the Nerve Injury, Ischemia, Soft-Tissue Injury, Skeletal Injury, Shock, and Age of Patient Score (NISSSA); and the Hannover Fracture Scale-97 (HFS-97) for ischemic and nonischemic limbs. The scores were analyzed in two ways: including and excluding limbs that required immediate amputation. RESULTS: The analysis did not validate the clinical utility of any of the lower-extremity injury-severity scores. The high specificity of the scores in all of the patient subgroups did confirm that low scores could be used to predict limb-salvage potential. The converse, however, was not true. The low sensitivity of the indices failed to support the validity of the scores as predictors of amputation. CONCLUSIONS: Lower-extremity injury-severity scores at or above the amputation threshold should be cautiously used by a surgeon who must decide the fate of a lower extremity with a high-energy injury.

Ipsilateral femoral neck and shaft fractures.

Ipsilateral femoral neck and shaft fractures are uncommon injuries that present a surgical challenge. Patients are relatively young, are usually victims of high-energy trauma, and have frequently sustained multisystem injuries. A comminuted midshaft femoral fracture secondary to axial loading should alert the treating physician to the possibility of an associated femoral neck fracture. This is important in light of the frequency of unrecognized ipsilateral femoral neck fractures. Several treatment options are described in the literature, but no clear consensus exists regarding the optimal treatment of these complex fractures. The authors contend that, given the potentially devastating complications of the femoral neck fracture in young patients (e.g., avascular necrosis, nonunion, and malunion), the neck fracture should be treated first and the shaft fracture second. The authors present an algorithm for the diagnosis and management of this injury based on a review of the literature, an understanding of the biology and severity of this injury, and the technical aspects of surgical treatment.

Posterior locked lateral compression injury of the pelvis: report of three cases.

Lateral compression injuries to the pelvis typically result in a rotationally unstable and vertically stable condition including an impaction and compression fracture of the posterior pelvic ring. The operative and postoperative management, as well as the morbidity and mortality, of these fractures differs significantly from vertical shear injuries to the pelvis, which are characterized by vertical and rotational instability. We report on three unusual lateral compression injuries to the pelvis, resulting in a complete disruption of the pelvic ring with vertical and rotational instability, by definition. Nevertheless, in these patients, locking of the posterior pelvic ring with medial translation of the iliac wing anterior to the sacrum resulted in a pseudostable condition. Their high rate of fracture-related associated injuries and possible complications, as well as the malalignment of the pelvis, required surgical restoration of the pelvic ring. Fracture reduction was successfully performed through an anterior approach in one patient and a posterior approach in two patients; the posterior approach was preferred. Open reduction and internal fixation of these pelvic ring fractures can result in a satisfactory outcome if the associated injuries are successfully dealt with.

Blood flow changes to the femoral head after acetabular fracture or dislocation in the acute injury and perioperative periods.

OBJECTIVES: Acute blood flow to the femoral head has been postulated to be affected negatively by traumatic acetabular fracture or dislocation. To the best of our knowledge, a prospective study that has examined acute changes in blood flow to the femoral head with respect to the timing of reduction and the effect of open reduction and internal fixation after acetabular fracture or dislocations has not been performed. DESIGN AND SETTING: From June 1994 to February 1996, fifty-four consecutive patients with hip dislocations with or without fractures of the acetabulum were entered into this investigation. The patients were categorized into three groups: isolated dislocations, fractures or dislocations requiring open reduction and internal fixation, and isolated acetabular fractures without dislocation but requiring open reduction and internal fixation. Single-photon emission computed tomography (SPECT) scans were obtained after relocations and preoperatively and postoperatively after open reduction and internal fixation of displaced acetabular fractures. RESULTS: The median dislocation time for all patients flow was 4.00 hours (range 1 to 24 hours). SPECT scanning showed a low blood flow pattern in five (9.25 percent) patients. A low blood flow pattern was seen in patients with early and late relocation times. Open reduction and internal fixation was not statistically associated with an avascular pattern of blood flow. Forty-two (78 percent) of our patients were available for follow-up, with an average of 24.3 months and a minimum of one year. There was one false-positive, one false-negative, and thirty-eight true-negative scans. CONCLUSIONS: A global loss of scintillation in the femoral head as determined by SPECT scanning occurs in some patients with hip dislocations and fractures or dislocations of the acetabulum in the early injury period. Changes in blood flow occurred in patients with short (one hour) and long (twenty-four hours) dislocation times. However, the development of avascular necrosis could not be predicted by early SPECT scanning. Until further multicenter studies are performed, SPECT scanning cannot be recommended on an acute or routine basis to predict those patients who will develop avascular necrosis. Operative approaches for open reduction of the hip and internal fixation of acetabular fractures do not appear to affect blood flow to the femoral head. Although a golden time to relocation cannot be fully established from this study, early relocation is advised to decrease the potential risk of vascular spasm, scarring, and subsequent avascular necrosis.

Osteocutaneous pedicle flap of the foot for salvage of below-knee amputation level after burn injury.

Lower extremity amputations are occasionally required after high-voltage electric and deep thermal burns. The extensive loss of skin and soft tissue after these injuries may make it difficult to fashion below-knee amputation that will readily tolerate a prosthesis. We have found an osteocutaneous pedicle fillet flap of the foot useful in the salvage of below-knee amputation after severe burn injury. Three patients have undergone this procedure after burn injury, 1 with burn secondary to high-voltage electric injury and 2 after deep thermal burns. All became ambulatory with artificial prostheses. There were no postoperative infections and no need for further revisions. The osteocutaneous pedicle fillet flap of the foot has proven to be a reliable form of below-knee stump coverage in patients with extensive soft tissue necrosis after burn injury.

Using polymer mats to biodegrade atrazine in groundwater: laboratory column experiments.

Large-scale column experiments were undertaken to evaluate the potential of in situ polymer mats to deliver oxygen into groundwater to induce biodegradation of the pesticides atrazine, terbutryn and fenamiphos contaminating groundwater in Perth, Western Australia. The polymer mats, composed of woven silicone (dimethylsiloxane) tubes and purged with air, were installed in 2-m-long flow-through soil columns. The polymer mats proved efficient in delivering dissolved oxygen to anaerobic groundwater. Dissolved oxygen concentrations increased from <0.2 mg l(-1) to approximately 4 mg l(-1). Degradation rates of atrazine in oxygenated groundwater were relatively high with a zero-order rate of 240-380 microg l(-1) or a first-order half-life of 0.35 days. Amendment with an additional carbon source showed no significant improvement in biodegradation rates, suggesting that organic carbon was not limiting biodegradation. Atrazine degradation rates estimated in the column experiments were similar to rates determined in laboratory culture experiments, using pure cultures of atrazine-mineralising bacteria. No significant degradation of terbutryn or fenamiphos was observed under the experimental conditions within the time frames of the study. Results from these experiments indicate that remediation of atrazine in a contaminated aquifer may be achievable by delivery of oxygen using an in situ polymer mat system.

Anterior sliding graft for tibiotalar arthrodesis.

The results using the anterior sliding graft technique with rigid internal fixation for tibiotalar arthrodesis were reviewed. The indications for anterior sliding graft technique included posttraumatic arthritis, rheumatoid arthritis, pseudarthrosis following prior attempt at arthrodesis, and postinfectious arthrosis. The arthrodesis rate was 95%. The overall prevalence of complications was 33%. The complications related to this method were minor and easily managed. The authors concluded that the anterior sliding graft technique is performed with readily available resources, has a high rate of union, and avoids the routine use of iliac bone graft.

Tarsometatarsal (Lisfranc's) fracture-dislocation.

Tarsometatarsal (Lisfranc's) fracture-dislocations account for 0.2% of all fractures. As many as 20% of these injuries are misdiagnosed or overlooked, especially in the polytrauma patient with other distracting injuries. The mechanism of injury, clinical diagnosis, treatment, and prognosis are reviewed. Results of arthrodesis of the tarsometatarsal joint for patients with symptomatic posttraumatic arthritis of the tarsometatarsal joint are discussed. A thorough understanding of this often misdiagnosed injury should facilitate the physician's prompt diagnosis and management of this potentially debilitating lesion, resulting in improved functional recovery for the patient.

Intraoperative complications during total hip arthroplasty.

Total hip replacement is one of the most common adult reconstructive procedures performed today. Even though training in total hip replacement has become fairly common in many orthopedic residency programs, complications can still occur during surgery. Preoperative planning and close attention to detail may prevent intraoperative problems. Awareness of the potential downfalls allows the surgeon to properly prepare for surgery, avoid intraoperative complications, and manage unavoidable problems when they do arise.

Soil gas carbon dioxide probe: laboratory testing and field evaluation.

An automated semi-continuous on-line instrument has been developed to measure CO2 gas concentrations in the vadose zone. The instrument uses semi-permeable polymer tubing (CO2 probe) for diffusion based sampling, coupled to an infra red sensor. The system operated automatically by intermittently purging the CO2 probe, which was installed in the vadose zone, with a non-CO2 gas at a low flow rate. The gas exiting the CO2 probe was monitored at the ground surface using a miniature infra red sensor and the response related to the vadose zone soil gas CO2 concentration. The in situ CO2 probes provided a reliable monitoring technique under long-term (18 months) aggressive and dynamic field conditions, with no interference observed from non-CO2 gases and volatile organic compounds. The probes provided data that were comparable to conventional grab sampling techniques without the labour-intensive sample collection and processing associated with these conventional techniques. Also, disturbance to vadose zone CO2 profiles from repeated grab samples during long-term semi-continuous monitoring could potential be reduced by using the diffusion based sampling technique.