Fundamental mode operation of a ribbon fiber laser by way of volume Bragg gratings.

Selection of the fundamental mode of an active large mode area "ribbon" fiber laser with core dimensions of 107.8 µm by 8.3 µm was produced by a transmitting Bragg grating (TBG) in a free-space resonator. The multimode performance of the original laser was characterized to have an M2 of 11.3 with an absorbed power slope efficiency of 76%. With the TBG aligned to provide maximum diffraction efficiency for the fundamental mode, the M2 improved to 1.45 at an absorbed power slope efficiency of 54% and enhanced the brightness by 5.1 times.

If a bird flies in the forest, does an insect hear it?

Birds are major predators of many eared insects including moths, butterflies, crickets and cicadas. We provide evidence supporting the hypothesis that insect ears can function as 'bird detectors'. First, we show that birds produce flight sounds while foraging. Eastern phoebes (Sayornis phoebe) and chickadees (Poecile atricapillus) generate broadband sounds composed of distinct repetitive elements (approx. 18 and 20 Hz, respectively) that correspond to cyclic wing beating. We estimate that insects can detect an approaching bird from distances of at least 2.5 m, based on insect hearing thresholds and sound level measurements of bird flight. Second, we show that insects with both high and low frequency hearing can hear bird flight sounds. Auditory nerve cells of noctuid moths (Trichoplusia ni) and nymphalid butterflies (Morpho peleides) responded in a bursting pattern to playbacks of an attacking bird. This is the first study to demonstrate that foraging birds generate flight sound cues that are detectable by eared insects. Whether insects exploit these sound cues, and alternatively, if birds have evolved sound-reducing foraging tactics to render them acoustically 'cryptic' to their prey, are tantalizing questions worthy of further investigation.

High energy femtosecond fiber chirped pulse amplification system with adaptive phase control.

We demonstrate increased peak power from an Yb fiber CPA system operating with strong self-phase modulation by shaping the spectral-phase of the input pulses. An adaptive control loop used feedback from the output autocorrelation. We investigated pre-compensation of both SPM phase distortion at high energies, and residual dispersion from mismatched stretcher/compressor technologies at low energies. Phase shaping resulted in improved pulse quality. When using a bulk grating stretcher, shaping increased the autocorrelation peak by a factor of 2.9, and with a fiber stretcher, shaping increased the autocorrelation peak by a factor of 3.4. High-quality 800 fs, 65 microJ recompressed pulses were produced. This technique could benefit a wide variety of fiber amplifier systems and is self-optimising for operation at both low and high pulse energies.

Grating-less, fiber-based oscillator that generates 25 nJ pulses at 80 MHz, compressible to 150 fs.

We report a passively mode-locked fiber-based oscillator that has no internal dispersion-compensating gratings. This design, which we believe to be the first of its kind, produces 25 nJ pulses at 80 MHz with the pulses compressible to 150 fs. The pulses appear to be self-similar and initial data imply that their energy is further scalable.

Acoustic startle/escape reactions in tethered flying locusts: motor patterns and wing kinematics underlying intentional steering.

We simultaneously recorded flight muscle activity and wing kinematics in tethered, flying locusts to determine the relationship between asymmetric depressor muscle activation and the kinematics of the stroke reversal at the onset of wing depression during attempted intentional steering manoeuvres. High-frequency, pulsed sounds produced bilateral asymmetries in forewing direct depressor muscles (M97, 98, 99) that were positively correlated with asymmetric forewing depression and asymmetries in stroke reversal timing. Bilateral asymmetries in hindwing depressor muscles (M127 and M128 but not M129) were positively correlated with asymmetric hindwing depression and asymmetries in the timing of the hindwing stroke reversal; M129 was negatively correlated with these shifts. Hindwing depressor asymmetries and wing kinematic changes were smaller and shifted in opposite direction than corresponding measurements of the forewings. These findings suggest that intentional steering manoeuvres employ bulk shifts in depressor muscle timing that affect the timing of the stroke reversals thereby establishing asymmetric wing depression. Finally, we found indications that locusts may actively control the timing of forewing rotation and speculate this may be a mechanism for generating steering torques. These effects would act in concert with forces generated by asymmetric wing depression and angle of attack to establish rapid changes in direction.

Auditory-evoked evasive manoeuvres in free-flying locusts and moths.

We presented free-flying locusts (Locusta migratoria L.) with sounds that varied in temporal structure and carrier frequency as they flew toward a light source in a flight room under controlled temperature and light conditions. Previous studies have shown tethered locusts react more often to trains of 30-kHz pulses than to pulse trains below 10 kHz. Further, this acoustic startle response has been suggested to function in bat-avoidance. We expected free-flying locusts to respond similarly; however, we found locusts responded to all sounds we presented, not just high-frequency, "bat-like" sounds. Response rates of turns, loops, and dives varied from 6% to 26% but were statistically independent of carrier frequency and/or pulse structure. Free-flying moths and tethered locusts were tested using a subset of our acoustic stimuli under the same temperature and light conditions as the free-flying locusts. Moth responses were carrier frequency dependent as were responses of tethered locusts positioned along the flight path observed in our free-flight trials. All responses were unaffected by a 90% reduction in room light. We conclude that locusts possess an acoustic startle response evocable in free flight, however, free-flying locusts do not show the same discrimination observed in tethered locusts under similar conditions.

Sound production and hearing in the blue cracker butterfly Hamadryas feronia (Lepidoptera, nymphalidae) from Venezuela.

Certain species of Hamadryas butterflies are known to use sounds during interactions with conspecifics. We have observed the behaviour associated with sound production and report on the acoustic characteristics of these sounds and on the anatomy and physiology of the hearing organ in one species, Hamadryas feronia, from Venezuela. Our observations confirm previous reports that males of this species will take flight from their tree perch when they detect a passing conspecific (male or female) and, during the chase, produce clicking sounds. Our analyses of both hand-held males and those flying in the field show that the sounds are short (approximately 0.5 s) trains of intense (approximately 80-100 dB SPL at 10 cm) and brief (2-3 ms) double-component clicks, exhibiting a broad frequency spectrum with a peak energy around 13-15 kHz. Our preliminary results on the mechanism of sound production showed that males can produce clicks using only one wing, thus contradicting a previous hypothesis that it is a percussive mechanism. The organ of hearing is believed to be Vogel's organ, which is located at the base of the forewing subcostal and cubital veins. Vogel's organ consists of a thinned region of exoskeleton (the tympanum) bordered by a rigid chitinous ring; associated with its inner surface are three chordotonal sensory organs and enlarged tracheae. The largest chordotonal organ attaches to a sclerite positioned near the center of the eardrum and possesses more than 110 scolopidial units. The two smaller organs attach to the perimeter of the membrane. Extracellular recordings from the nerve branch innervating the largest chordotonal organ confirm auditory sensitivity with a threshold of 68 dB SPL at the best frequency of 1.75 kHz. Hence, the clicks with peak energy around 14 kHz are acoustically mismatched to the best frequencies of the ear. However, the clicks are broad-banded and even at 1-2 kHz, far from the peak frequency, the energy is sufficient such that the butterflies can easily hear each other at the close distances at which they interact (less than 30 cm). In H. feronia, Vogel's organ meets the anatomical and functional criteria for being recognized as a typical insect tympanal ear.

Riding the Ice Age El Nino? Pacific biogeography and evolution of Metrosideros subg. Metrosideros (Myrtaceae) inferred from nuclear ribosomal DNA.

Metrosideros subg. Metrosideros (Myrtaceae) comprises approximately 26 species distributed widely across the Pacific basin. They occur on the ancient Gondwanan landmasses of New Zealand and New Caledonia, as well as on the volcanic islands of the remote Pacific, from Melanesia to tropical Polynesia and the Bonin Island. Phylogenetic analysis based on nuclear ribosomal DNA spacer sequences from all named species showed Metrosideros umbellata of New Zealand as basal in the subgenus, with the remaining species falling into three monophyletic clades. One includes the seven New Caledonian species together with three daughters in western Oceania that probably dispersed during the mid/late Tertiary. A second contains six taxa located in east Melanesia and Samoa that may also have arisen from a mid/late Tertiary dispersal, in this instance from New Zealand. The third includes three New Zealand endemics along with all of the taxa in remote Polynesia and accounts for much of the total range of the subgenus. These dispersed taxa in Polynesia either are identical to the New Zealand species Metrosideros excelsa or differ by a single nucleotide change. We suggest that they are all derived from a Pleistocene dispersal out of New Zealand. A relatively recent dispersal is surprising, given that this wind-dispersed genus has occupied New Zealand for much of the Tertiary and that some of the islands in remote Polynesia date to at least the Miocene. We attribute this dramatic range expansion to climate change-specifically changes in wind flow patterns-in the southern hemisphere during worldwide glaciation.

Bat-deafness in day-flying moths (Lepidoptera, Notodontidae, Dioptinae).

Assuming that bat-detection is the primary function of moth ears, the ears of moths that are no longer exposed to bats should be deaf to echolocation call frequencies. To test this, we compared the auditory threshold curves of 7 species of Venezuelan day-flying moths (Notodontidae: Dioptinae) to those of 12 sympatric species of nocturnal moths (Notodontidae: Dudusinae, Noctuidae and Arctiidae). Whereas 2 dioptines (Josia turgida, Zunacetha annulata) revealed normal ears, 2 (J. radians, J. gopala) had reduced hearing at bat-specific frequencies (20-80 kHz) and the remaining 3 (Thirmida discinota, Polypoetes circumfumata and Xenorma cytheris) revealed pronounced to complete levels of high-frequency deafness. Although the bat-deaf ears of dioptines could function in other purposes (e.g., social communication), the poor sensitivities of these species even at their best frequencies suggest that these moths represent a state of advanced auditory degeneration brought about by their diurnal life history. The phylogeny of the Notodontidae further suggests that this deafness is a derived (apomorphic) condition and not a retention of a primitive (pleisiomorphic), insensitive state.

Is complete laparoscopic colectomy superior to laparoscopic assisted colectomy?

Much debate has centered around what constitutes a true laparoscopic colon resection. Purists argue that intracorporeal division of the mesentery and anastomosis confer a benefit over a "laparoscopic assisted" procedure. The aim of this study was to further examine this issue. Data were prospectively collected on 102 consecutive laparoscopic colon resections. Five procedures were converted to open cases and were excluded from analysis. Procedures were divided into two groups. Group 1 (n = 34) consisted of complete laparoscopic procedures (no abdominal incision was made): abdominoperineal resection (3), Hartmann's reversal (3), end colostomy (7), low anterior resection (5), proctectomy (1), sigmoid colectomy (15). Group 2 (n = 63) consisted of laparoscopic "assisted" procedures (i.e., an incision was made to facilitate anastomosis, division of the mesentery, and/or specimen retrieval): Ileocolic resection (6), restorative proctocolectomy (26), right colectomy (19), subtotal colectomy/end ileostomy (5), subtotal colectomy/ileorectal anastomosis (7). Length of hospitalization and duration of postoperative ileus were compared. A subset analysis of right colectomy (intracorporeal mobilization and extracorporeal division of the mesentery and anastomosis) versus sigmoid colectomy (intracorporeal mobilization, division of the mesentery and anastomosis) was also performed. There were no statistically significant differences in length of hospital stay (Group 1, 7.47 +/- 2.75 days; Group 2, 7.78 +/- 5.55 days) or duration of postoperative ileus (Group 1, 3.24 +/- 1.56 days; Group 2, 3.68 +/- 1.58 days). Similarly, in the sigmoid colectomy versus right colectomy subset analysis, there were no statistically significant differences in length of hospital stay (sigmoid colectomy, 7.92 +/- 2.90 days; right colectomy, 6.40 +/- 1.50 days) or duration of postoperative ileus (sigmoid colectomy, 3.36 +/- 1.39 days; right colectomy, 3.18 +/- 1.07 days). Our data demonstrate that intracorporeal division of the mesentery and anastomosis confer no advantage over the laparoscopic assisted procedures. Data were prospectively collected on 102 consecutive laparoscopic colon resections. There were no statistically significant differences in length of hospital stay or duration of postoperative ileus regardless of whether intracorporeal or extracorporeal mesenteric division and anastomosis were undertaken. These data demonstrate that a completely laparoscopic procedure does not appear to offer any advantage as compared to a laparoscopic assisted one.

Principles of adjuvant therapy.

The use of an additional modality to improve surgical treatment of cancer is well established when dealing with some cancers but controversial with others. The reasons for this are complex, not least because the biological mechanisms by which tumour growth and metastasis occur are still imperfectly understood. This article summarises the most important applications of adjuvant therapy, with particular reference to breast and colorectal cancer.

Preoperative ultrasound to predict technical difficulties and complications of laparoscopic cholecystectomy.

Thirty-five patients with symptomatic gallbladder disease were prospectively evaluated by ultrasound the day before laparoscopic cholecystectomy. Diminished gallbladder function and wall thickening were significantly associated with increased technical difficulty of the operation (Student's t-test, P < 0.001). There was no association between gallbladder volume or number of calculi and operative difficulty. Dilated common bile ducts were detected by ultrasound in five patients (14%) and bile duct calculi in two patients (6%). Ultrasound findings can be used as predictors of potential operative difficulties when selecting patients for laparoscopic cholecystectomy. Ultrasound should be used as an initial screening investigation to detect common bile duct dilatation and calculi.

Prospective comparison of laparoscopic and conventional anterior resection.

A prospective comparison of laparoscopically assisted (n = 11) and conventional (n = 14) anterior resection in patients with sigmoid colon or upper rectal cancer was carried out. Patients were not randomized; age and the presence of metastases determined the type of surgery. Laparoscopic assistance was used to mobilize the tumour and minimize the abdominal incision. This was achieved in all patients and six of the 11 required only a muscle-splitting incision. The mean(s.d.) operating time was longer for laparoscopic than conventional surgery (205(31) versus 123(26) min, P = 0.01). The mean(s.d.) time to reintroduction of normal diet (2.5(0.2) versus 3.6(0.3) days, P = 0.01), postoperative analgesia requirement (2.6(0.4) versus 7.4(2.1) doses of pethidine, P = 0.01) and length of hospital stay (12.3(3) versus 14.3(6) days, P = 0.08) were less in the laparoscopic group. Histopathological examination of the resection specimens showed similar results for the two procedures. Major complications were few and occurred in a similar proportion of patients treated laparoscopically or conventionally. Laparoscopically assisted anterior resection is technically feasible, adequate tumour excision can be achieved and recovery after operation is enhanced.

Laparoscopic versus open appendicectomy: prospective randomised trial.

Randomised assessment of new laparoscopic surgical techniques is difficult. Surgeons need time to become experienced with the methods and tend, when they have experience, to favour one or other approach. We have carried out a prospective randomised comparison of laparoscopic and conventional appendicectomy done by surgeons of comparable experience in patients with suspected acute appendicitis. Postoperative management decisions were made by surgeons other than the operating surgeon. 140 patients were randomly assigned to open (OA) or laparoscopic (LA) appendicectomy (70 each). The age, sex ratio, duration of symptoms, and proportion of patients with histologically confirmed appendicitis was similar in the two groups. Operating time was longer for LA than for OA (mean 70.3 [SD 21.9] vs 46.5 [25.9] min; p < 0.001). There were no major intraoperative complications in either group. 14 (20%) patients in the LA group required conversion to an open operation. No significant differences between the groups were found postoperatively for pain score, analgesic requirement, time to reintroduction of diet, or hospital stay. 46 LA patients and 42 OA patients attended follow-up 3 weeks after surgery. Similar proportions had returned to work (36 [79%] vs 31 [74%]). The frequency of wound complications and wound pain after leaving hospital was lower after LA but not significantly so. We conclude that the postoperative course after LA and conventional OA does not differ significantly.

The gleaning attacks of the northern long-eared bat, Myotis septentrionalis, are relatively inaudible to moths.

This study empirically tests the prediction that the echolocation calls of gleaning insectivorous bats (short duration, high frequency, low intensity) are acoustically mismatched to the ears of noctuid moths and are less detectable than those of aerially hawking bats. We recorded auditory receptor cell action potentials elicited in underwing moths (Catocala spp.) by echolocation calls emitted during gleaning attacks by Myotis septentrionalis (the northern long-eared bat) and during flights by the aerial hawker Myotis lucifugus (the little brown bat). The moth ear responds inconsistently and with fewer action potentials to the echolocation calls emitted by the gleaner, a situation that worsened when the moth's ear was covered by its wing (mimicking a moth resting on a surface). Calls emitted by the aerial-hawking bat elicited a significantly stronger spiking response from the moth ear. Moths with their ears covered by their wings maintained their relative hearing sensitivity at their best frequency range, the range used by most aerial insectivorous bats, but showed a pronounced deafness in the frequency range typically employed by gleaning bats. Our results (1) support the prediction that the echolocation calls of gleaners are acoustically inconspicuous to the ears of moths (and presumably other nocturnal tympanate insects), leaving the moths particularly vulnerable to predation, and (2) suggest that gleaners gain a foraging advantage against eared prey.

Linewidth and frequency jitter measurement of an erbium-doped fiber ring laser by using a loss-compensated, delayed self-heterodyne interferometer.

The single-mode linewidth of an erbium-doped, single-frequency, fiber ring laser has been measured by using a newly developed loss-compensated delayed self-heterodyne interferometer that has a resolution of less than 600 Hz. The natural linewidth is determined to have an upper bound of less than 2 kHz. In addition, frequency jitter was found to be dominant over the natural mately 4 kHz.