Optimal heating rate in constant pressure and constant flow gas chromatography.

Optimal heating rate is the one resulting in the shortest analysis time for achieving a required separation performance of a column. The previously recommended default heating rate (RT,Def ) was optimal for temperature-programmed gas chromatography analyses in constant pressure mode. It has been shown herein that the same recommendation can be extended to constant flow mode with fixed heating rate (RT ). The numerical value of RT,Def has been herein rescaled from previous 10 ∘ C / t M (10°C per void time) where tM was measured at 50°C, to 12 ∘ C / t M with tM measured at 150°C-a round number in the middle of the gas chromatography temperature range, chosen as a reference temperature for numerical values of all temperature-dependent gas chromatography parameters. It has been experimentally found based on theory developed herein that R T , Def = 12 ∘ C / t M is optimal for columns with φ = 0.001 ( φ = d f / d is dimensionless film thickness, d and df  are the column internal diameter and film thickness, respectively) in constant pressure mode and constant flow mode with fixed RT . Theory shows that, for arbitrary φ, R T , Def = 12 ( 1000 φ ) 0.09 ∘ C / t M . The theory also shows that the fixed RT is optimal for constant pressure mode. In constant flow mode, however, the optimal RT should gradually increase with increasing temperature (T). The optimal theoretical curves RT (T), different for different flow rates, were found. However, only the optimization of the fixed RT was experimentally evaluated due to limited capability of existing gas chromatography instrumentation and resources. It has been shown that the separation-time tradeoff in constant pressure mode is slightly better than that in constant flow mode. The experimental data are compiled in the Supporting information.

Rapid Facial Cryotherapy for Combat Sports: A Comparison of Materials and Methods for Cooling Facial Tissues in 60 Seconds or Less.

CONTEXT: Athletes in combat sports who have sustained facial hematomas during competition have traditionally been treated with an enswell. These treatments take place between rounds of the competition and generally last less than 60 seconds. The efficacy of this modality has not been studied. Other modalities may provide a more effective cryotherapy treatment in this timeframe. OBJECTIVE: To compare the efficacy of different forms of rapid cryotherapy to cause surface temperature changes of the face within 60 seconds of application. DESIGN: Crossover study. SETTING: Laboratory. PARTICIPANTS: Eleven healthy men (age 21.73 [1.42] y, mass 82.1 [5.6] kg, height 177.2 [7.0] cm). INTERVENTIONS: A 60-second treatment using chilled surgical steel enswell, copper, commercial cold pack, aluminum, brass, ice cube, ice pack, and saltwater pack. MAIN OUTCOME MEASURES: Preintervention and postintervention surface facial temperatures. RESULTS: The ice bag, cold pack, ice cube, saltwater pack, and stainless-steel enswell caused statistically different temperatures preintervention to postintervention. The ice bag and saltwater pack cause statistically greater cooling than the other materials tested. CONCLUSIONS: This study does not support the clinical use of an enswell to provide short-duration cryotherapy treatments to facial tissue, as ice packs are more effective.

The Effect of Elevation on Intramuscular Tissue Temperatures.

CONTEXT: Ice, compression, and elevation, or ICE, is a widely used treatment for acute musculoskeletal injuries. The effects of ice and compression on tissue temperatures have been established, but whether elevation during cryotherapy affects temperature change has not. Elevation has potential to alter local perfusion and thereby alter the balance of heat loss/heat gain, potentially impacting tissue cooling during cryotherapy. OBJECTIVE: To measure the effect and interaction of ice, compression, and elevation on intramuscular temperatures. We hypothesized that elevation would not have an effect on intramuscular tissue temperature. DESIGN: Randomized crossover study design. SETTING: University athletic training facility. PATIENTS OR OTHER PARTICIPANTS: A total of 15 healthy volunteers (age 20.93 [1.67] y) provided informed consent and participated. INTERVENTIONS: Participants completed 8 treatment conditions: no treatment (control), ice only (I), compression only (C), elevation only (E), ice and compression (IC), ice and elevation (IE), compression and elevation (CE), or ice, compression, and elevation (ICE). All conditions were tested on each participant with a minimum of 48 hours between each condition. Intramuscular temperatures were recorded every 30 seconds during a 1-minute preapplication, 30-minute treatment, and 20-minute postapplication period. MAIN OUTCOME MEASURES: The temperature difference between the mean treatment temperature and the mean preapplication temperature was compared across each measurement depth and treatment condition. RESULTS: Non-ice treatments (control, C, E, and CE; means 33.4, 34.5, 33.7, and 34.6, respectively) had warmer intramuscular temperatures than any treatment that included ice (I, IC, IE, and ICE; means 28.4, 19.8, 28.0, and 19.3, respectively). There were no differences between IC and ICE (means 19.8 and 19.3, respectively). Ice alone was different from everything (Control, C, E, IC, CE, and ICE) except IE Conclusions: Elevation does not appear to play a role in temperature changes during cryotherapy treatments.

The Effectiveness of Cervical Strengthening in Decreasing Neck-Injury Risk in Wrestling.

Clinical Scenario: In wrestling, athletes often support a large amount of weight on their heads or are forced into extreme ranges of motion. These suboptimal movement conditions lead to a high prevalence of neck injuries in wrestlers. A large portion of the work done by the cervical musculature in wrestling is theorized to be eccentric or isometric types of contractions. Strengthening of these cervical muscles is clinically considered to play a vital role in being competitive on the wrestling mat. The cervical stability provided by strengthening these muscles may also play a part in injury prevention among wrestlers. Focused Clinical Question: Does increased cervical strength lead to a decreased risk of injury in wrestling? Summary of Search, "Best Evidence" Appraised, and Key Findings: The literature was searched for studies of level 4 evidence or higher using the Oxford Centre for Evidence-Based Medicine level of evidence system that investigated the relationship between cervical strength and injury risk in wrestling. No studies were found comparing cervical strength to injury risk in wrestling, but 2 related studies were found and have been included in this critically appraised topic. Clinical Bottom Line: There is poor evidence to support a relationship between cervical strength and injury risk in wrestling. Strength of Recommendation: There is grade C evidence to indicate that increased cervical strength decreases the risk of injury in wrestling.

Ultrasound mediated destruction of multifunctional microbubbles for image guided delivery of oxygen and drugs.

We synthesized multifunctional activatible microbubbles (MAMs) for ultrasound mediated delivery of oxygen and drugs with both ultrasound and fluorescence imaging guidance. Oxygen enriched perfluorocarbon (PFC) compound was encapsulated in liposome microbubbles (MBs) by a modified emulsification process. DiI dye was loaded as a model drug. The ultrasound targeted microbubble destruction (UTMD) process was guided by both ultrasonography and fluorescence imaging modalities. The process was validated in both a dialysis membrane tube model and a porcine carotid artery model. Our experiment results show that the UTMD process effectively facilitates the controlled delivery of oxygen and drug at the disease site and that the MAM agent enables ultrasound and fluorescence imaging guidance of the UTMD process. The proposed MAM agent can be potentially used for UTMD-mediated combination therapy in hypoxic ovarian cancer.

Evaluation of conditions of comprehensive two-dimensional gas chromatography that yield a near-theoretical maximum in peak capacity gain.

The peak capacity gain (Gn) of a GC×GC system is the ratio of the system peak capacity to that of an optimized one-dimensional GC analysis lasting the same time and providing the same detection limit. A near-theoretical maximum in Gn has been experimentally demonstrated in GC×GC-TOF based on a 60m×0.25mm primary column. It was found that Gn was close to 9 compared to the theoretical maximum of about 11 for this system. A six-sigma peak capacity of 4500 was obtained during an 80min heating ramp from 50°C to 320°C. Using peak deconvolution, 2242 individual peaks were determined in a Las Vegas runoff water sample. This is the first definitive experimental demonstration known to us of an order-of-magnitude Gn. The key factors enabling this gain were: relatively sharp (about 20ms at half height) reinjection pulses into the secondary column, relatively long (60m) primary column, the same diameters in primary and secondary columns, relatively low retention factor at the end of the secondary analysis (k≅5 instead of 15, optimal for ideal conditions), optimum flow rate in both columns, and helium (rather than hydrogen) used as the carrier gas. The latter, while making the analysis 65% longer than if using H2, was a better match to the reinjection bandwidth and cycle time.

A method of aligning peak lists generated by gas chromatography high-resolution mass spectrometry.

We report a method for the peak list alignment of gas chromatography high resolution time-of-flight mass spectrometry data. The alignment is performed in a z-score transformed retention time domain to standardize chromatographic peak distribution across samples. A mixture score is developed to assess the similarity between two peaks by simultaneously evaluating the mass spectral similarity and the closeness of retention time. An analysis of experimental data acquired under three different flow rates indicates that the proposed method is able to correctly align the heterogeneous data. The effectiveness of method is further validated by analyzing experimental data of multiple mixtures of metabolite extract from mouse liver with 28 spiked-in acids. All of the detected spiked-in acids were correctly aligned. A statistical test correctly detected the concentration differences of the spiked-in compounds between sample groups using the alignment table. The area under curve (AUC) value in the receiver operating characteristic (ROC) curve is larger than 0.85 in all three of the compared sample groups, indicating a high accuracy of peak alignment and supporting the potential application of the proposed method for metabolomics projects such as biomarker discovery.

Progression of secondary injury after musculoskeletal trauma-a window of opportunity?

CONTEXT: Acute musculoskeletal-injury management largely focuses on inhibiting secondary injury, although the data describing secondary injury and the timeline for its progression are sparse. OBJECTIVE: To describe the timeline and early progression of secondary injury in skeletal muscle over the first 5 h after blunt trauma. DESIGN: A controlled laboratory study with 2 independent variables (injury status and postinjury time point) in a 2 × 21 factorial. SETTING: University research laboratory. SUBJECTS: 168 male Sprague Dawley rats (250 to 275 g). INTERVENTIONS: Uniform blunt-contusion injury was caused to the right triceps surae using a drop-weight method; the contralateral limb served as an uninjured control. Both triceps surae were excised and flash frozen at 21 intervals across 5 h postinjury (8 animals, each 15 min). MAIN OUTCOME MEASURES: Cytochrome-c oxidase activity via reduction of triphenyltetrazolium chloride (TTC) to triphenylformazan. RESULTS: There was an interaction effect (P = .041) between and main effects for both injury status (P < .0005) and postinjury time point (P = .038). In the first 30 min after injury, uninjured tissues did not differ from injured tissues, and both displayed TTC reduction rates in the vicinity of 7.1 ± 0.94 µg × mg-1 × h-1. Statistical differences between uninjured and injured tissues became evident starting at 30 min. TTC reduction for uninjured tissues did not change, but injured tissues declined in a roughly linear fashion across the entire 5-h period to 4.8 ± 1.04 µg × mg-1 × h-1. CONCLUSIONS: Cytochrome-c oxidase activity, an indicator of oxidative phosphorylation and mitochondrial viability, is diminished by events that follow muscle trauma. Loss of this enzymatic activity becomes statistically evident at 30 min postinjury and continues linearly for at least 5 h. This suggests that secondary injury is a slowly developing problem of more than 5 h duration. A window of opportunity for intervention may lie somewhere within the first 30 min after injury.

Therapeutic ultrasound decreases mechano-growth factor messenger ribonucleic acid expression after muscle contusion injury.

OBJECTIVE: To examine the influence of nonthermal ultrasound on mechano-growth factor (MGF) messenger ribonucleic acid (mRNA) expression after blunt trauma. DESIGN: A 2x4 factorial multivariate analysis of variance design. SETTING: University research laboratory. ANIMALS: Thirty-six 3- to 4-month-old male Wistar rats (mean weight, 280.8+/-21.5g). Thirty-two received a bilateral contusion injury to the gastrocnemius via a drop mass technique. Four were control animals. INTERVENTION: Ultrasound treatment (frequency, 3MHz; intensity, 0.3W/cm(2); continuous duty cycle) was started 24 hours postinjury and delivered for 5 minutes daily on 4 consecutive days. Treatment was on the left hindlimb and the contralateral right hindlimb was the nonultrasound control. MAIN OUTCOME MEASURES: Muscle mass (in grams) and MGF mRNA expression as measured via real-time reverse transcriptase polymerase chain reaction. RESULTS: Ultrasound had no effect on muscle mass (F(1,28)=2.723, P=.110, 1-beta=.357, eta(2)=.089). Ultrasound treatments decreased MGF mRNA expression in the treated limb compared with the nontreated hindlimb (F(1,28)=6.605, P=.016, 1-beta=.699, eta(2)=.191). CONCLUSIONS: The nonthermal ultrasound treatments resulted in decreased MGF mRNA expression after blunt trauma to the gastrocnemius muscles.

The dual roles of neutrophils and macrophages in inflammation: a critical balance between tissue damage and repair.

OBJECTIVE: To discuss the acute phase of inflammatory response with a focus on the neutrophilic response and its role in inflammation. We discuss the relative balance between the need for inflammation to stimulate repair and the need to limit inflammation because of the additional damage it causes. DATA SOURCES: We conducted a MEDLINE search from 1966 to 2005 for literature related to acute inflammation, muscle injury, and repair using combinations of the key words inflammation, neutrophil, macrophage, and cytokines. Additional literature was acquired through cross-referencing of bibliographies of articles obtained through the MEDLINE searches. DATA SYNTHESIS: We reviewed more than 200 relevant articles. Although neutrophils are an important cell population in acute inflammation, few athletic trainers are familiar with the neutrophil's actions or its dichotomous role as both perpetrator of tissue damage and initiator of repair. Neutrophils dominate the early stages of inflammation and set the stage for repair of tissue damage by macrophages. These actions are orchestrated by numerous cytokines and the expression of their receptors, which represent a potential means for inhibiting selective aspects of inflammation. CONCLUSIONS: Neutrophils infiltrate injured tissues but can also be present after noninjurious exercise. These cells have both specific and nonspecific defensive immune system functions that can cause tissue damage in isolation or as sequelae to other tissue injury. It might seem that limiting the action of neutrophils would be clinically beneficial, but these cells are also responsible for initiating the reparative process that is later managed by macrophages. Although achieving a therapeutic balance between limiting inflammation and stimulating repair is important, the duplicitous roles of neutrophils and macrophages in both the inflammation and healing processes create a physiologic paradox for clinicians whose goals are to limit inflammation and to stimulate healing after acute soft tissue injury.

Nonthermal ultrasound and exercise in skeletal muscle regeneration.

OBJECTIVE: To determine whether continuous nonthermal therapeutic ultrasound (US) and low-intensity exercise (Ex) influence skeletal muscle regeneration after a standardized contusion injury in an animal model. DESIGN: Randomized controlled trial with blinded comparisons in a 2 x 2 factorial (US by Ex) design. SETTING: Animal care facility and exercise physiology biochemistry laboratory. ANIMALS: Twenty male Wistar rats (age, 8 mo) received a reproducible bilateral contusion injury to the gastrocnemius muscles. Ten gastrocnemius muscles from 5 noninjured, nontreated rats provided baseline control data. INTERVENTIONS: US (continuous duty cycle, 3 MHz; intensity, 0.1 W/cm2 ; transducer, 1cm2 ; duration, 5 min/d; duty cycle, 100%) and exercise (20 min/d of low-intensity treadmill walking at 14 m/min). Gastrocnemius muscles from injured rats received exercise treatment alone (Ex + NoUS), exercise and US treatment (Ex + US), US treatment alone (NoEx + US), and no treatment (NoEx + NoUS). MAIN OUTCOME MEASURES: Ninety-six-hour postinjury muscle mass, contractile protein concentration, fiber cross-sectional area, number of nuclei per fiber, and myonuclear density. RESULTS: Myonuclei per fiber were statistically greater in injured than in noninjured gastrocnemius muscle (P < .05). There were no statistical differences (P > .01) among the 4 injured treatment groups for any of the outcome measures chosen as biomarkers of skeletal muscle regeneration. CONCLUSIONS: There is no evidence that the specific continuous US and Ex protocols investigated enhanced skeletal muscle regeneration after contusion injury.

Three-MHz Ultrasound Heats Deeper Into the Tissues Than Originally Theorized.

OBJECTIVE: To measure muscle temperature of ultrasound at 1-MHz and 3-MHz frequencies at a depth of 2.5 cm and to compare treatment durations for vigorous heating (increase of 4 degrees C) and for heating to 40 degrees C. DESIGN AND SETTING: A counterbalanced, repeated-measures design with 1 fixed, independent variable, 1.5-W/cm(2) ultrasound treatment (1 MHz, 3 MHz, or control [sham]) using a Theratouch 7.7 ultrasound device. Dependent variables were end-treatment temperature at 2.5 cm, time to vigorous heating, and time to reach 40 degrees C. SUBJECTS: Eighteen healthy volunteers (age = 24.6 +/- 2.3 years, height = 173.0 +/- 9.7 cm, mass = 72.0 +/- 16.3 kg) without a history of lower leg injury. MEASUREMENTS: The medial triceps surae intramuscular temperature at 2.5 cm was measured every 10 seconds using an implantable thermocouple. Each of the 3 ultrasound frequencies was applied in counterbalanced order at 24-hour intervals. RESULTS: Ultrasound of 3 MHz produced both vigorous heating (at 3.4 minutes) and an absolute temperature of 40 degrees C (at 4 minutes). CONCLUSIONS: Our results suggest that 3-MHz ultrasound heats 0.5 cm deeper than suggested by others. With our machine, 3-MHz ultrasound was more effective in heating muscle at this depth than 1-MHz ultrasound.

Pre-athletic training students perform better on written tests with teacher-centered instruction.

There are many different methods of instruction used in the academic setting. Little experimental research exists examining which mode is more effective in educating students. The purpose of this study was to compare scores obtained on the written and the practical examinations of students on a single topic taught through either a teacher-centered format or a student-centered format. A 2 x 2 x 6 factorial design was used in this study. Independent variables were teaching style (teacher-centered instruction and student-centered instruction), order (first or second), and learning style (competitive, collaborative, participant, avoidant, dependent, and independent). The dependent variables were the scores obtained on a written and a practical examination of gait and crutch fitting. Forty pre-athletic training students in their first semester of their first year (16 males, 24 females) participated in this study. The Grasha-Reichmann Student Learning Style Scale was used to determine the learning styles of the subjects. The total subject pool was divided randomly into two groups, one taught by teacher-centered instruction and the other by student-centered instruction. Both groups took the same written and practical examinations, and scores were recorded. A 2 x 2 x 6 fixed model multivariate analysis of variance was performed. A difference was observed for teaching style (F2,21 = 5.35, p = 0.01), on the combination of written and practical exam scores. A difference also was observed on the written examination scores with the teacher-centered format producing better results (p < 0.05); but teacher-centered format scores did not differ from student-centered scores on the practical examination (p > 0.05). Teacher-centered instruction improves written test performance compared with student-centered instruction. When initially teaching a skill, direct teacher involvement may help students learn and perform better.

The effects of land vs. aquatic plyometrics on power, torque, velocity, and muscle soreness in women.

The purpose of this study was to compare changes in performance indicators (power, torque, and velocity) and muscle soreness between plyometric training on land and in water. Thirty-two college age women were randomly assigned to 8 weeks of an identical plyometric training program on land or in an aquatic setting. Performance indicators were assessed pretraining, midtraining, and posttraining. Muscle soreness (ordinal scale) and pain sensitivity (palpation) were assessed after a training bout (0, 48, and 96 hours) during the first week of training and when training intensity was increased (weeks 3 and 6). Performance indictors increased for both groups (pretraining < midtraining < posttraining, p < or = 0.001). Muscle soreness was significantly greater in the land compared to the aquatic plyometric training group at baseline and each time training intensity was increased, p = 0.01. Aquatic plyometrics provided the same performance enhancement benefits as land plyometrics with significantly less muscle soreness.

Intercollegiate student athlete use of nutritional supplements and the role of athletic trainers and dietitians in nutrition counseling.

A survey of university student athletes was conducted to determine supplement use, perceived efficacy of supplements, availability and use of nutrition services, and perceived nutrition knowledge of athletic trainers. Results from 236 athletes showed that 88% used one or more nutritional supplements, yet perceived efficacy was moderate (2.9 or less; 5-point scale). Classes (69.4%), brochures (75%), and individual counseling (47%) were available and were used by 29.9%, 33.2%, and 17.9% of athletes, respectively. Primary sources of nutrition information were athletic trainers (39.8%), strength and conditioning coaches (23.7%), and dietitians (14.4%). Athletes perceived athletic trainers to have strong nutrition knowledge (mean=3.8+/-0.9; 5-point scale). Many (23.5%) did not know whether a dietitian was available. Dietitians must accelerate their marketing efforts to student athletes, work closely with athletic trainers to provide sound nutrition information, and provide services that meet the needs of a diverse population of student athletes.

Identical 3-MHz ultrasound treatments with different devices produce different intramuscular temperatures.

STUDY DESIGN: A counterbalanced, repeated-measures design with ultrasound device (Omnisound 3000C, Dynatron 950, Excel Ultra III) as the independent variable. The 2 dependent variables were intramuscular (IM) temperature at 6 minutes and at the end of a 10-minute treatment. OBJECTIVE: To compare IM temperatures produced by identical 3-MHz ultrasound treatments between 3 different ultrasound devices. BACKGROUND: Most recent studies prescribing intensity and duration parameters for thermal ultrasound treatments have been performed using an Omnisound device, but have not been verified in other common ultrasound devices. METHODS AND MEASURES: Six uninjured volunteers (mean age +/- SD, 22 +/- 3.4 y; mean height +/- SD, 171.9 +/- 11.0 cm; mean mass +/- SD, 66.1 +/- 11.1 kg) gave informed consent and served as subjects. Separate ultrasound treatments using identical parameters (3 MHz, 1.5 W/cm2, 10 minutes, treatment area equal to twice transducer surface area) were administered at 24 or 48 hours intervals using a different ultrasound device for each treatment. Left medial calf IM temperature was recorded every 20 seconds using implantable thermocouples at a depth of 1.6 cm below the treatment surface. Data were analyzed using MANOVA with Sidak adjusted multiple comparisons post hoc. RESULTS: Tissue heating using the Omnisound device was greater than with either the Dynatron or the Excel. The results of treatments using Dynatron or Excel devices did not differ. The Omnisound was the only device to consistently produce IM temperatures above the 40 degrees C therapeutic threshold and did so in less than 6 minutes. The other devices did not reach this threshold within the 10-minute treatment session. Subjects routinely reported heating sensations approaching discomfort when the IM temperature reached the 40 degrees C therapeutic threshold. CONCLUSIONS: Because there are differences in thermal effects between ultrasound devices, our results suggest that recently published parameters for ultrasound intensity and duration parameters will not produce equally therapeutic effects for all ultrasound devices.